Interlocking Puzzles

This section covers interlocking puzzles - wherein multiple pieces fit together such that the puzzle does not fall apart, and presents a challenge to disassemble and re-assemble. This is one of my favorite categories.

Here are my groupings:

Traditional 6-Piece Burrs

Any story about interlocking puzzles has to start with the traditional six-piece burr puzzle. Like other well-known puzzles, it has acquired a probably-fanciful backstory, and is known by several names, including the "puzzle knot," the "Devil's Knot" (Teufelsknoten in German), "Chinese Cross," the "Lock of Luban" (Luban Suo) or the "Lock of Kongming" (Kongming Suo). Stewart Coffin's The Puzzling World of Polyhedral Dissections hosted on John Rausch's site is a great introduction to this type of puzzle. Martin Gardner discusses burrs briefly (as an introduction to the puzzle sculptures of Miguel Berrocal) in his 1989 book Penrose Tiles to Trapdoor Ciphers, and most of the key puzzle authors mention the puzzle. There have been sporadic fits of research into the six-piece burr, including an extensive analysis by hand by the Dutch mathematician J. H. de Boer, and work by Tom O'Beirne and Arthur Cross, but Bill Cutler has performed the definitive computer analysis, and the statistics cited below are based on his analysis.

The earliest relevant U.S. Patent seems to be 1225760 - Brown 1917. However, a traditional six-piece burr appears in Hoffmann's 1893 classic "Puzzles Old and New" in Chapter III as No. XXXVI "The Nut (or Six-piece) Puzzle." Jerry Slocum and Dieter Gebhardt put together a compendium of puzzle advertisements found in the 1785 catalogue of the merchant Peter Friedrich Catel, who established a retail store in Berlin in 1780. The 1785 catalogue contains an ad for a traditional six-piece burr puzzle called "The Small Devil's Hoof" (in addition to an ad for the Large Devil's Hoof which is a 24-piece cage burr). In Stewart Coffin's Geometric Puzzle Design, Stewart discusses the six-piece burr in chapter 7, and reports that Jerry Slocum's New Findings on the History of the Six Piece Burr traces the six-piece burr back to Germany in 1698.

There is a distinction made between burr puzzles that contain no internal "holes" or voids - termed "solid" burrs, and those that do contain one or more - termed "holey" burrs. Also, there is a distinction made among the pieces which can be produced without hard-to-manufacture blind (or internal) corners versus those that cannot. The 59 "easy" pieces are called "notchable" and there are only 25 of them that can be used to build solid burrs. Those 25 pieces can be put together in 314 ways. There are 369 general pieces that can be used to produce 119,979 solid burrs. Of those 369, 112 can be used in duplicate and 2 in triplicate, making a useful set of 485 pieces. The 59 notchable pieces can be used to make 13,354,991 assemblies, most of which are holey. Overall, there are 837 pieces that can be used to produce an estimated 5.95 billion constructible puzzles.

So, to make a traditional six-piece burr, six pieces, usually but not always distinct, are selected from the overall set of 837 possible such pieces, and interlocked in a characteristic 2x2x2 pattern along 3 orthogonal axes - see the photo at upper left. The burr shape is tricky to envision without an example in front of one, but it gets easier with practice.

Bill Cutler has done extensive analysis on both the "holey" six-piece burr and all six-piece burrs in general, and Bill offers several burrs for sale. Jurg von Kanel created the wonderful Burr Puzzles Site hosted at IBM Research. Jurg's site offers a solution analyzer applet and historical info about burrs. Bruno Curfs' site offers additional analysis. Ed Pegg wrote a good survey article about burrs. Peter Roesler's site also discusses burr puzzles, and has an interesting history of Willem van der Poel's Grandfather 6x6x6 burr. You can see some burrs at John Rausch's Puzzleworld and at Wayne Daniel's site. You can use Andreas Roever's Burr Tools and Andre van Kammen's Puzzlesolver 3D to model, solve, and design burr puzzles.

If you're interested in collecting 6-piece burrs, I suggest you first check out the "Puzzle Will Be Played" site to get some idea of the variety available. Look under "Interlocking (6 piece burr: traditional)." Though they may be sold under different names and by different vendors, burr puzzles that use the same set of six pieces are isomorphic and have identical solutions (although using pieces longer than six units might eliminate some solutions). That site also provides a comprehensive catalogue of burr pieces.

The "level" of a burr puzzle is the number of distinct moves (a shift of one or more pieces as a unit, usually by one unit in one direction) that must be performed to remove the first piece or pieces - there can be a concatenation of figures usually separated by dots - these are the numbers of steps to remove successive pieces. All solid burrs are level 1 - they come apart without any preliminary shifting. Burrs with internal holes, of which there can be from 1 to 20, can achieve higher levels, and one goal of research has been to delimit what is possible in terms of level complexity.

I admit that, early on, I didn't like burr puzzles. But as I read more about them, and tried various designs, my appreciation for them grew. I put together the diagram below to try to summarize and organize some of the facts I learned about this category of puzzle.

The 25 Notchable Pieces Used in Solid Burrs

Shown below is the set of 25 pieces referred to above (these are depicted as length-6; for longer pieces simply extend the 2x2 solid burr equally on each end). I have located some of them out of numerical sequence, to show mirror images together. This guide will help you determine if two puzzles are equivalent.

Over the years, different researchers and writers have employed different schemes to identify the pieces. I use Jurg von Kanel's numbering system and I have adapted some of the ASCII character piece diagrams below from his documents. I created a "Burr ID Tool" in JavaScript which will display an ASCII character picture of any given burr - you just check off the particular cubelets that are present in the piece. (These character-based renderings rely on fixed-width fonts and won't display well on some devices, particularly phones - at some point I'll have to create images for the pieces.)

The first letter, in bold, is the "standard" letter ID for the piece. The second letter is as assigned by Curfs and is also used by Wayne Daniel. The third letter, if present, is that assigned by Edwin Wyatt in "Puzzles in Wood." A 'p' suffix indicates the piece is included in the Professor burr set. The last number is the usual count of this piece in 42-piece sets that allow you to construct 314 solid burrs.

I have lately given names to some of the pieces, which I find more helpful than the letters or numbers when trying to remember sets of pieces I have seen before.

Piece #1 is the "key" piece. Piece 1024 (Y) is the "minimal" piece - no more material can be removed without the piece falling apart.


1 A A A [p] 1
    +----+----+----+----+----+----+
   /                             /|
  +                             + |
 /                             /  +
+----+----+----+----+----+----+   |
|                             |   |
|                             |   +
+                             +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    
The Key
18 B B L [p] 2
    +----+    +----+----+----+----+
   /    /|   /                   /|
  +    + |  +                   + |
 /    /  +-/                   /  +
+----+  / +----+----+----+----+   |
|    | +  |                   |   |
|    |/   |                   |   +
+    +----+                   +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    
35 C E 1
    +----+----+    +----+----+----+
   /         /|   /              /|
  +         + |  +              + |
 /         /  +-/              /  +
+----+----+  / +----+----+----+   |
|         | +  |              |   |
|         |/   |              |   +
+         +----+              +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    
52 D P J [p] 2
    +----+         +----+----+----+
   /    /|        /              /|
  +    + |       +              + |
 /    /  +----+-/              /  +
+----+  /      +----+----+----+   |
|    | +       |              |   |
|    |/        |              |   +
+    +----+----+              +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    
The Side Tray
103 F S H 1
    +----+----+         +----+----+
   /         /|        /         /|
  +         + |       +         + |
 /         /  +---+--/         /  +
+----+----+  /      +----+----+   |
|         | +       |         |   |
|         |/        |         |   +
+         +----+----+         +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    
The Half-Tray
120 G U 1
    +----+              +----+----+
   /    /|             /         /|
  +    + |            +         + |
 /    /  +----+---+--/         /  +
+----+  /           +----+----+   |
|    | +            |         |   |
|    |/             |         |   +
+    +----+----+----+         +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    
The Three-Quarters Tray
256 J X B [p2] 3
    +----+                   +----+
   /    /|                  /    /|
  +    + |                 +    + |
 /    /  +----+----+----+-/    /  +
+----+  /                +----+   |
|    | +                 |    |   |
|    |/                  |    |   +
+    +----+----+----+----+    +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    
The Tray
86 E H 1
    +----+    +----+    +----+----+
   /    /|   /    /|   /         /|
  +    + |  +    + |  +         + |
 /    /  +-/    /  +-/         /  +
+----+  / +----+  / +----+----+   |
|    | +  |    | +  |         |   |
|    |/   |    |/   |         |   +
+    +----+    +----+         +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    
154 H K I [p] 1
    +----+    +----+----+    +----+
   /    /|   /         /|   /    /|
  +    + |  +         + |  +    + |
 /    /  +-/         /  +-/    /  +
+----+  / +----+----+  / +----+   |
|    | +  |         | +  |    |   |
|    |/   |         |/   |    |   +
+    +----+         +----+    +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    
The Toaster
188 I M M [p] 2
    +----+         +----+    +----+
   /    /|        /    /|   /    /|
  +    + |       +    + |  +    + |
 /    /  +----+-/    /  +-/    /  +
+----+  /      +----+  / +----+   |
|    | +       |    | +  |    |   |
|    |/        |    |/   |    |   +
+    +----+----+    +----+    +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    
The (Bottle) Opener
871 M T K 2
    +----+----+         +----+----+
   /         /|        /         /|
  +         + |       +         + |
 /         /  +----+-/         /  +
+----+----+  /      +----+----+   |
|         | +----+--|         |   |
|         | |       |         |   +
+         + |       +         +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
The Barbells
928 V L D 2
    +----+    +----+----+    +----+
   /    /|   /         /|   /    /|
  +    + |  +----+----+ |  +    + |
 /    /  +--|         | +-/    /  +
+----+  /   |         |/ +----+   |
|    | +    +         +  |    |   |
|    |/    /|        /   |    |   +
+    +----+ |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
The Tongue
1024 Y Y F [p2] 3
    +----+                   +----+
   /    /|                  /    /|
  +    + |                 +    + |
 /    /  +----+----+----+-/    /  +
+----+  /                +----+   |
|    | +    +----+----+  |    |   |
|    |/    /|        /   |    |   +
+    +----+ |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
The Y
792 R D 2
    +----+    +----+----+----+----+
   /    /|   /                   /|
  +    + |  +----+----+         + |
 /    /  +--|        /         /  +
+----+  /   |       +----+----+   |
|    | +    +       |         |   |
|    |/    /|       |         |   +
+    +----+ |       +         +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
911 N C G 2
    +----+----+----+----+    +----+
   /                   /|   /    /|
  +         +----+----+ |  +    + |
 /         /|         | +-/    /  +
+----+----+ |         |/ +----+   |
|         | +         +  |    |   |
|         | |        /   |    |   +
+         + |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
824 T R C [p] 2
    +----+         +----+----+----+
   /    /|        /              /|
  +    + |       +----+         + |
 /    /  +----+--|   /         /  +
+----+  /        |  +----+----+   |
|    | +    +----+  |         |   |
|    |/    /|       |         |   +
+    +----+ |       +         +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
975 O Q E [p] 2
    +----+----+----+         +----+
   /              /|        /    /|
  +         +----+ |       +    + |
 /         /|    | +----+-/    /  +
+----+----+ |    |/      +----+   |
|         | +    +----+  |    |   |
|         | |        /   |    |   +
+         + |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
888 U W 2
    +----+              +----+----+
   /    /|             /         /|
  +    + |            +         + |
 /    /  +----+----+-/         /  +
+----+  /           +----+----+   |
|    | +    +----+--|         |   |
|    |/    /|       |         |   +
+    +----+ |       +         +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
1007 Q V 2
    +----+----+              +----+
   /         /|             /    /|
  +         + |            +    + |
 /         /  +----+----+-/    /  +
+----+----+  /           +----+   |
|         | +----+----+  |    |   |
|         | |        /   |    |   +
+         + |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
The Walls The Offsets The Clubs
960 X N 2
    +----+         +----+    +----+
   /    /|        /    /|   /    /|
  +    + |       +----+ |  +    + |
 /    /  +-------|    | +-/    /  +
+----+  /        |    |/ +----+   |
|    | +    +----+    +  |    |   |
|    |/    /|        /   |    |   +
+    +----+ |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
992 W O [p] 2
    +----+    +----+         +----+
   /    /|   /    /|        /    /|
  +    + |  +----+ |       +    + |
 /    /  +--|    | +----+-/    /  +
+----+  /   |    |/      +----+   |
|    | +    +    +----+  |    |   |
|    |/    /|        /   |    |   +
+    +----+ |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
359 L F 1
    +----+----+----+    +----+----+
   /              /|   /         /|
  +         +----+ |  +         + |
 /         /|    | +-/         /  +
+----+----+ |    |/ +----+----+   |
|         | +    +--|         |   |
|         | |       |         |   +
+         + |       +         +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
615 K G 1
    +----+----+    +----+----+----+
   /         /|   /              /|
  +         + |  +----+         + |
 /         /  +--|   /         /  +
+----+----+  /   |  +----+----+   |
|         | +----+  |         |   |
|         | |       |         |   +
+         + |       +         +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
856 S J 1
    +----+    +----+    +----+----+
   /    /|   /    /|   /         /|
  +    + |  +----+ |  +         + |
 /    /  +--|    | +-/         /  +
+----+  /   |    |/ +----+----+   |
|    | +    +    +--|         |   |
|    |/    /|       |         |   +
+    +----+ |       +         +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
943 P I 1
    +----+----+    +----+    +----+
   /         /|   /    /|   /    /|
  +         + |  +----+ |  +    + |
 /         /  +--|    | +-/    /  +
+----+----+  /   |    |/ +----+   |
|         | +----+    +  |    |   |
|         | |        /   |    |   +
+         + |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
The Fingers The Notched Half-Trays The Fingered Clubs

Selected Other Burr Pieces

The following are only a small selection of additional pieces, used in some of the burrs mentioned below. Many of these pieces have internal corners and are more difficult to manufacture. Remember, there are 837 pieces in total - if you want to see them all, you'd best visit Ishino's site.

56
    +----+         +----+----+----+
   /    /|        /              /|
  +    + |       +----+         + |
 /    /  +----+--|   /         /  +
+----+  /        |  +----+----+   |
|    | +         +--|         |   |
|    |/             |         |   +
+    +----+----+----+         +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    

Triple Slide
72
    +----+----+----+    +----+----+
   /              /|   /         /|
  +    +----+----+ |  +         + |
 /    /|         | +-/         /  +
+----+ |         |/ +----+----+   |
|    | +----+----+  |         |   |
|    |/             |         |   +
+    +----+----+----+         +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    

Interrupted Slide
88
    +----+    +----+    +----+----+
   /    /|   /    /|   /         /|
  +    + |  +----+ |  +         + |
 /    /  +--|    | +-/         /  +
+----+  /   |    |/ +----+----+   |
|    | +    +----+  |         |   |
|    |/             |         |   +
+    +----+----+----+         +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    
Piston, Hordern,
Dozen, BB31-10-40
94
    +----+    +----+    +----+----+
   /    /|   /    /|   /         /|
  +    + |  +    + |  +----+    + |
 /    /  +-/    /  +--|   /    /  +
+----+  / +----+  /   |  +----+   |
|    | +  |    | +    +--|    |   |
|    |/   |    |/        |    |   +
+    +----+    +----+----+    +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    

Triple Slide
109
    +----+----+         +----+----+
   /         /|        /         /|
  +         +----+    +----+    + |
 /              /|----|   /    /  +
+----+----+----+ |    |  +----+   |
|              | +    +--|    |   |
|              |/        |    |   +
+              +----+----+    +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    

BCL6000
112
    +----+----+         +----+----+
   /         /|        /         /|
  +    +----+ |       +----+    + |
 /    /|    | +-------|   /    /  +
+----+ |    |/        |  +----+   |
|    | +----+         +--|    |   |
|    |/                  |    |   +
+    +----+----+----+----+    +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    

Interrupted Slide
126
    +----+              +----+----+
   /    /|             /         /|
  +    + |  +----+    +----+    + |
 /    /  +-/    /|----|   /    /  +
+----+  / +----+ |    |  +----+   |
|    | +  |    | +    +--|    |   |
|    |/   |    |/        |    |   +
+    +----+    +----+----+    +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    

STC#36
128
    +----+              +----+----+
   /    /|             /         /|
  +    + |            +----+    + |
 /    /  +------------|   /    /  +
+----+  /             |  +----+   |
|    | +              +--|    |   |
|    |/                  |    |   +
+    +----+----+----+----+    +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    

Hedgehog, Kaldeway
156
    +----+    +----+----+    +----+
   /    /|   /         /|   /    /|
  +    + |  +----+    + |  +    + |
 /    /  +--|   /    /  +-/    /  +
+----+  /   |  +----+  / +----+   |
|    | +    +--|    | +  |    |   |
|    |/        |    |/   |    |   +
+    +----+----+    +----+    +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    

Triple Slide
160
    +----+    +----+----+    +----+
   /    /|   /         /|   /    /|
  +    + |  +----+----+ |  +    + |
 /    /  +--|         | +-/    /  +
+----+  /   |         |/ +----+   |
|    | +    +----+----+  |    |   |
|    |/                  |    |   +
+    +----+----+----+----+    +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    

(many)
192
    +----+         +----+    +----+
   /    /|        /    /|   /    /|
  +    + |       +----+ |  +    + |
 /    /  +----+--|    | +-/    /  +
+----+  /        |    |/ +----+   |
|    | +         +----+  |    |   |
|    |/                  |    |   +
+    +----+----+----+----+    +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    

#G
224
    +----+    +----+         +----+
   /    /|   /    /|        /    /|
  +    + |  +----+ |       +    + |
 /    /  +--|    | +----+-/    /  +
+----+  /   |    |/      +----+   |
|    | +    +----+       |    |   |
|    |/                  |    |   +
+    +----+----+----+----+    +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    

JVK, Millable 5.4
412
    +----+    +----+----+    +----+
   /    /|   /         /|   /    /|
  +    + |  +----+    + |  +    + |
 /    /  +--|   /    /  +-/    /  +
+----+  /   |  +----+  / +----+   |
|    | +    +  |    | +  |    |   |
|    |/    /|  |    |/   |    |   +
+    +----+ |  +    +----+    +  / 
|         | +--|              | +  
|         |/   |              |/   
+----+----+    +----+----+----+    

(many)
448
    +----+         +----+    +----+
   /    /|        /    /|   /    /|
  +    + |       +----+ |  +    + |
 /    /  +----+--|    | +-/    /  +
+----+  /        |    |/ +----+   |
|    | +    +----+----+  |    |   |
|    |/    /|   /        |    |   +
+    +----+ |  +----+----+    +  / 
|         | +--|              | +  
|         |/   |              |/   
+----+----+    +----+----+----+    

Interrupted Slide
736
    +----+    +----+         +----+
   /    /|   /    /|        /    /|
  +    + |  +----+ |       +    + |
 /    /  +--|    | +----+-/    /  +
+----+  /   |    |/      +----+   |
|    | +    +----+----+  |    |   |
|    |/         /|   /   |    |   +
+    +----+----+ |  +----+    +  / 
|              | +--|         | +  
|              |/   |         |/   
+----+----+----+    +----+----+    

BCL6000, #G
464
    +----+----+----+         +----+
   /              /|        /    /|
  +    +----+----+ |       +    + |
 /    /|         | +----+-/    /  +
+----+ |         |/      +----+   |
|    | +----+    +       |    |   |
|    |/    /|   /        |    |   +
+    +----+ |  +----+----+    +  / 
|         | +--|              | +  
|         |/   |              |/   
+----+----+    +----+----+----+    

Brown's
576
    +----+         +----+----+----+
   /    /|        /              /|
  +    + |       +----+----+    + |
 /    /  +----+--|        /    /  +
+----+  /        |       +----+   |
|    | +         +    +--|    |   |
|    |/         /|   /   |    |   +
+    +----+----+ |  +----+    +  / 
|              | +--|         | +  
|              |/   |         |/   
+----+----+----+    +----+----+    

D. Kriz II
511
    +----+                   +----+
   /    /|                  /    /|
  +    +----+              +    + |
 /         /|-+----+----+-/    /  +
+----+----+ |            +----+   |
|         | +----+       |    |   |
|         | |   /        |    |   +
+         + |  +----+----+    +  / 
|         | +--|              | +  
|         |/   |              |/   
+----+----+    +----+----+----+    

Interrupted Slide,
#D, F#73
476
    +----+    +----+         +----+
   /    /|   /    /|        /    /|
  +    + |  +----+----+    +    + |
 /    /  +--|   /    /|-+-/    /  +
+----+  /   |  +----+ |  +----+   |
|    | +    +  |    | +  |    |   |
|    |/    /|  |    |/   |    |   +
+    +----+ |  +    +----+    +  / 
|         | +--|              | +  
|         |/   |              |/   
+----+----+    +----+----+----+    

Prog. Nightmare
702
    +----+         +----+    +----+
   /    /|        /    /|   /    /|
  +    + |  +----+----+ |  +    + |
 /    /  +-/    /|    | +-/    /  +
+----+  / +----+ |    |/ +----+   |
|    | +  |    | +    +  |    |   |
|    |/   |    | |   /   |    |   +
+    +----+    + |  +----+    +  / 
|              | +--|         | +  
|              |/   |         |/   
+----+----+----+    +----+----+    

BC-CCU10, Mega-6
512
    +----+                   +----+
   /    /|                  /    /|
  +    + |                 +    + |
 /    /  +----+----+----+-/    /  +
+----+  /                +----+   |
|    | +    +----+       |    |   |
|    |/    /|   /        |    |   +
+    +----+ |  +----+----+    +  / 
|         | +--|              | +  
|         |/   |              |/   
+----+----+    +----+----+----+    

(many)
768
    +----+                   +----+
   /    /|                  /    /|
  +    + |                 +    + |
 /    /  +----+----+----+-/    /  +
+----+  /                +----+   |
|    | +         +----+  |    |   |
|    |/         /|   /   |    |   +
+    +----+----+ |  +----+    +  / 
|              | +--|         | +  
|              |/   |         |/   
+----+----+----+    +----+----+    

(many)
551
    +----+----+    +----+----+----+
   /         /|   /              /|
  +         + |  +----+         + |
 /         /  +--|   /         /  +
+----+----+  /   |  +----+----+   |
|         | +    +  |         |   |
|         |/    /|  |         |   +
+         +----+ |  +         +  / 
|              | +--|         | +  
|              |/   |         |/   
+----+----+----+    +----+----+    

BC-L5N
624
    +----+----+         +----+----+
   /         /|        /         /|
  +    +----+ |       +----+    + |
 /    /|    | +----+--|   /    /  +
+----+ |    |/        |  +----+   |
|    | +----+    +----+--|    |   |
|    |/         /|   /   |    |   +
+    +----+----+ |  +----+    +  / 
|              | +--|         | +  
|              |/   |         |/   
+----+----+----+    +----+----+    

BC-CCU10
704
    +----+         +----+    +----+
   /    /|        /    /|   /    /|
  +    + |       +----+ |  +    + |
 /    /  +----+--|    | +-/    /  +
+----+  /        |    |/ +----+   |
|    | +         +    +  |    |   |
|    |/         /|   /   |    |   +
+    +----+----+ |  +----+    +  / 
|              | +--|         | +  
|              |/   |         |/   
+----+----+----+    +----+----+    

(many)
499
    +----+                   +----+
   /    /|                  /    /|
  +    +----+    +----+----+    + |
 /         /|-+-/              /  +
+----+----+ |  +----+----+----+   |
|         | +--|              |   |
|         | |  |              |   +
+         + |  +              +  / 
|         | +--|              | +  
|         |/   |              |/   
+----+----+    +----+----+----+    

BC-CC5H
757
    +----+                   +----+
   /    /|                  /    /|
  +    +----+----+    +----+    + |
 /              /|-+-/         /  +
+----+----+----+ |  +----+----+   |
|              | +--|         |   |
|              | |  |         |   +
+              + |  +         +  / 
|              | +--|         | +  
|              |/   |         |/   
+----+----+----+    +----+----+    

Prog. Nightmare
760
    +----+                   +----+
   /    /|                  /    /|
  +    + |            +----+    + |
 /    /  +----+----+-/         /  +
+----+  /           +----+----+   |
|    | +         +--|         |   |
|    |/         /|  |         |   +
+    +----+----+ |  +         +  / 
|              | +--|         | +  
|              |/   |         |/   
+----+----+----+    +----+----+    

Baffling, Brother
800
    +----+    +----+----+----+----+
   /    /|   /                   /|
  +    + |  +----+----+----+    + |
 /    /  +--|             /    /  +
+----+  /   |            +----+   |
|    | +    +         +--|    |   |
|    |/    /|        /   |    |   +
+    +----+ |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    

Brown's
820
    +----+         +----+----+----+
   /    /|        /              /|
  +    + |       +              + |
 /    /  +----+-/              /  +
+----+  /      +----+----+----+   |
|    | +    +--|              |   |
|    |/    /|  |              |   +
+    +----+ |  +----+         +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    

STC#36
832
    +----+         +----+----+----+
   /    /|        /              /|
  +    + |       +----+----+    + |
 /    /  +----+--|        /    /  +
+----+  /        |       +----+   |
|    | +    +----+    +--|    |   |
|    |/    /|        /   |    |   +
+    +----+ |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    

Brown's, G4
976
    +----+----+----+         +----+
   /              /|        /    /|
  +    +----+----+ |       +    + |
 /    /|         | +----+-/    /  +
+----+ |         |/      +----+   |
|    | +----+    +----+  |    |   |
|    |/    /|        /   |    |   +
+    +----+ |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    

D. Kriz II, Enigma, #G
880
    +----+----+         +----+----+
   /         /|        /         /|
  +    +----+ |       +----+    + |
 /    /|    | +----+--|   /    /  +
+----+ |    |/        |  +----+   |
|    | +----+----+----+--|    |   |
|    |/    /|        /   |    |   +
+    +----+ |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    

Dubois/Gaby
883
    +----+              +----+----+
   /    /|             /         /|
  +    +----+    +----+         + |
 /         /|-+-/              /  +
+----+----+ |  +----+----+----+   |
|         | +--|              |   |
|         | |  |              |   +
+         + |  +----+         +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    

BC-CCU10
922
    +----+    +----+----+    +----+
   /    /|   /         /|   /    /|
  +    + |  +         + |  +    + |
 /    /  +-/         /  +-/    /  +
+----+  / +----+----+  / +----+   |
|    | +  |         | +  |    |   |
|    |/   |         |/   |    |   +
+    +----+----+----+----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    

Piston
926
    +----+    +----+----+    +----+
   /    /|   /         /|   /    /|
  +    + |  +    +----+ |  +    + |
 /    /  +-/    /|    | +-/    /  +
+----+  / +----+ |    |/ +----+   |
|    | +  |    | +    +  |    |   |
|    |/   |    |/    /   |    |   +
+    +----+----+    +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    

BC-CC5H
956
    +----+         +----+    +----+
   /    /|        /    /|   /    /|
  +    + |       +    + |  +    + |
 /    /  +----+-/    /  +-/    /  +
+----+  /      +----+  / +----+   |
|    | +    +--|    | +  |    |   |
|    |/    /|  |    |/   |    |   +
+    +----+ |  +----+----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    

Prog. Nightmare,
BC-CC4H
990
    +----+    +----+         +----+
   /    /|   /    /|        /    /|
  +    + |  +    + |       +    + |
 /    /  +-/    /  +----+-/    /  +
+----+  / +----+  /      +----+   |
|    | +  |    | +----+  |    |   |
|    |/   |    |/    /   |    |   +
+    +----+----+    +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    

Interrupted Slide
996
    +----+----+              +----+
   /         /|             /    /|
  +    +----+ |  +----+----+    + |
 /    /|    | +-/              /  +
+----+ |    |/ +----+----+----+   |
|    | +----+--|              |   |
|    |/    /|  |              |   +
+    +----+ |  +----+         +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    

Baffling
1008
    +----+----+              +----+
   /         /|             /    /|
  +    +----+ |            +    + |
 /    /|    | +----+----+-/    /  +
+----+ |    |/           +----+   |
|    | +----+----+----+  |    |   |
|    |/    /|        /   |    |   +
+    +----+ |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    

(many)
1015
    +----+                   +----+
   /    /|                  /    /|
  +    +----+         +----+    + |
 /         /|-+----+-/         /  +
+----+----+ |       +----+----+   |
|         | +----+--|         |   |
|         | |       |         |   +
+         + |       +         +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    

(many)
1021
    +----+                   +----+
   /    /|                  /    /|
  +    +----+----+         +    + |
 /              /|-+----+-/    /  +
+----+----+----+ |       +----+   |
|              | +----+  |    |   |
|              |/    /   |    |   +
+         +----+    +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    

Prog. Nightmare

Some Common Six-Piece Burr Designs

I have noticed the following four designs recur over and over again in different products. You should be able to find examples fairly easily, and these four are a reasonable introduction to the category.

The Diabolical Structure
1 A A [p]
    +----+----+----+----+----+----+
   /                             /|
  +                             + |
 /                             /  +
+----+----+----+----+----+----+   |
|                             |   |
|                             |   +
+                             +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    
The Key
256 J X [p2]
    +----+                   +----+
   /    /|                  /    /|
  +    + |                 +    + |
 /    /  +----+----+----+-/    /  +
+----+  /                +----+   |
|    | +                 |    |   |
|    |/                  |    |   +
+    +----+----+----+----+    +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    
The Tray
256 J X [p2]
    +----+                   +----+
   /    /|                  /    /|
  +    + |                 +    + |
 /    /  +----+----+----+-/    /  +
+----+  /                +----+   |
|    | +                 |    |   |
|    |/                  |    |   +
+    +----+----+----+----+    +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    
The Tray
256 J X [p2]
    +----+                   +----+
   /    /|                  /    /|
  +    + |                 +    + |
 /    /  +----+----+----+-/    /  +
+----+  /                +----+   |
|    | +                 |    |   |
|    |/                  |    |   +
+    +----+----+----+----+    +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    
The Tray
928 V L
    +----+    +----+----+    +----+
   /    /|   /         /|   /    /|
  +    + |  +----+----+ |  +    + |
 /    /  +--|         | +-/    /  +
+----+  /   |         |/ +----+   |
|    | +    +         +  |    |   |
|    |/    /|        /   |    |   +
+    +----+ |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
The Tongue
928 V L
    +----+    +----+----+    +----+
   /    /|   /         /|   /    /|
  +    + |  +----+----+ |  +    + |
 /    /  +--|         | +-/    /  +
+----+  /   |         |/ +----+   |
|    | +    +         +  |    |   |
|    |/    /|        /   |    |   +
+    +----+ |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
The Tongue

This set of pieces appeared in a French puzzle (I don't have) called "Charpente Diabolique" (the Diabolical Structure). The pieces include: 1, 3x256, and 2x928 (AJ-VV-JJ or ALLXXX). The burr I have from "Melissa & Doug" uses the same set. It is very easy to construct - in fact this is possibly the easiest of all 6-piece burrs.

 

The Ivory Chinese Cross
1 A A [p]
    +----+----+----+----+----+----+
   /                             /|
  +                             + |
 /                             /  +
+----+----+----+----+----+----+   |
|                             |   |
|                             |   +
+                             +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    
The Key
256 J X [p2]
    +----+                   +----+
   /    /|                  /    /|
  +    + |                 +    + |
 /    /  +----+----+----+-/    /  +
+----+  /                +----+   |
|    | +                 |    |   |
|    |/                  |    |   +
+    +----+----+----+----+    +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    
The Tray
824 T R [p]
    +----+         +----+----+----+
   /    /|        /              /|
  +    + |       +----+         + |
 /    /  +----+--|   /         /  +
+----+  /        |  +----+----+   |
|    | +    +----+  |         |   |
|    |/    /|       |         |   +
+    +----+ |       +         +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
The
975 O Q [p]
    +----+----+----+         +----+
   /              /|        /    /|
  +         +----+ |       +    + |
 /         /|    | +----+-/    /  +
+----+----+ |    |/      +----+   |
|         | +    +----+  |    |   |
|         | |        /   |    |   +
+         + |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
Offsets
928 V L
    +----+    +----+----+    +----+
   /    /|   /         /|   /    /|
  +    + |  +----+----+ |  +    + |
 /    /  +--|         | +-/    /  +
+----+  /   |         |/ +----+   |
|    | +    +         +  |    |   |
|    |/    /|        /   |    |   +
+    +----+ |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
The Tongue
1024 Y Y [p2]
    +----+                   +----+
   /    /|                  /    /|
  +    + |                 +    + |
 /    /  +----+----+----+-/    /  +
+----+  /                +----+   |
|    | +    +----+----+  |    |   |
|    |/    /|        /   |    |   +
+    +----+ |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
The Y


This small plastic red burr is one of my older puzzles - I don't recall where I got it. It uses the following pieces: 1, 256, 824/975, 928, 1024. This set of pieces has been used often, and has appeared in ivory. Jurg von Kaenel refers to this as "the well-known one."

Reiss 1974 Licorice Stix

This is a small plastic burr pendant, made in China.

This set also appeared as "Dohikus." (I don't have this.)

 

The Six-Way Set
52 D P [p]
    +----+         +----+----+----+
   /    /|        /              /|
  +    + |       +              + |
 /    /  +----+-/              /  +
+----+  /      +----+----+----+   |
|    | +       |              |   |
|    |/        |              |   +
+    +----+----+              +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    
The Side Tray
792 R D
    +----+    +----+----+----+----+
   /    /|   /                   /|
  +    + |  +----+----+         + |
 /    /  +--|        /         /  +
+----+  /   |       +----+----+   |
|    | +    +       |         |   |
|    |/    /|       |         |   +
+    +----+ |       +         +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
The
911 N C
    +----+----+----+----+    +----+
   /                   /|   /    /|
  +         +----+----+ |  +    + |
 /         /|         | +-/    /  +
+----+----+ |         |/ +----+   |
|         | +         +  |    |   |
|         | |        /   |    |   +
+         + |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
Walls
824 T R [p]
    +----+         +----+----+----+
   /    /|        /              /|
  +    + |       +----+         + |
 /    /  +----+--|   /         /  +
+----+  /        |  +----+----+   |
|    | +    +----+  |         |   |
|    |/    /|       |         |   +
+    +----+ |       +         +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
The
975 O Q [p]
    +----+----+----+         +----+
   /              /|        /    /|
  +         +----+ |       +    + |
 /         /|    | +----+-/    /  +
+----+----+ |    |/      +----+   |
|         | +    +----+  |    |   |
|         | |        /   |    |   +
+         + |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
Offsets
1024 Y Y [p2]
    +----+                   +----+
   /    /|                  /    /|
  +    + |                 +    + |
 /    /  +----+----+----+-/    /  +
+----+  /                +----+   |
|    | +    +----+----+  |    |   |
|    |/    /|        /   |    |   +
+    +----+ |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
The Y


I got this aluminum burr called "Rainbow" from Bits and Pieces - it came in a nice black drawstring pouch. It was designed by Paul Eibe. It uses the following pieces: 52, 792/911, 824/975, 1024. This is the only notchable, voidless set that can be put together six different ways.

This is DNORTY from Pentangle. The name derives from the bold piece letters given in my table above. It uses the same set of pieces as the Rainbow: 52 (D), 911 (N), 975 (O), 792 (R), 824 (T), 1024 (Y).

This is a Toyo Glass puzzle called "Tongari Kun and Roppongi." Not only is there a burr, but it must be assembled inside the glass container. The mouth is too small to pass the burr in fully assembled form. Remember, there are 6 different ways to construct this burr - you must find one that permits construction within the container!

This set was sold some time ago as "The Zoozzler." (I don't have it.)

To resolve all six different solutions, I found it helpful to ask myself, "What sits in the notch of piece #52, and then which piece is opposite #52?" I found the following:

  1. left offset 824, right offset 975 - two 3-pc halves slide together
  2. right offset 975, left offset 824 - mirror of the above
  3. right wall 911, left offset 824
  4. right wall 911, left wall 792
  5. left wall 792, right offset 975
  6. left wall 792, right wall 911

 

The Yamato Block
1 A A [p]
    +----+----+----+----+----+----+
   /                             /|
  +                             + |
 /                             /  +
+----+----+----+----+----+----+   |
|                             |   |
|                             |   +
+                             +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    
The Key
188 I M [p]
    +----+         +----+    +----+
   /    /|        /    /|   /    /|
  +    + |       +    + |  +    + |
 /    /  +----+-/    /  +-/    /  +
+----+  /      +----+  / +----+   |
|    | +       |    | +  |    |   |
|    |/        |    |/   |    |   +
+    +----+----+    +----+    +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    
The (Bottle) Opener
824 T R [p]
    +----+         +----+----+----+
   /    /|        /              /|
  +    + |       +----+         + |
 /    /  +----+--|   /         /  +
+----+  /        |  +----+----+   |
|    | +    +----+  |         |   |
|    |/    /|       |         |   +
+    +----+ |       +         +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
The
975 O Q [p]
    +----+----+----+         +----+
   /              /|        /    /|
  +         +----+ |       +    + |
 /         /|    | +----+-/    /  +
+----+----+ |    |/      +----+   |
|         | +    +----+  |    |   |
|         | |        /   |    |   +
+         + |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
Offsets
1024 Y Y [p2]
    +----+                   +----+
   /    /|                  /    /|
  +    + |                 +    + |
 /    /  +----+----+----+-/    /  +
+----+  /                +----+   |
|    | +    +----+----+  |    |   |
|    |/    /|        /   |    |   +
+    +----+ |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
The Y
1024 Y Y [p2]
    +----+                   +----+
   /    /|                  /    /|
  +    + |                 +    + |
 /    /  +----+----+----+-/    /  +
+----+  /                +----+   |
|    | +    +----+----+  |    |   |
|    |/    /|        /   |    |   +
+    +----+ |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
The Y


This is the Yamato Block puzzle. This burr uses pieces nos. 1, 188, 824/975, and 2x 1024.

This is "No. P19 Joe's Puzzle" from Wm. F. Drueke & Sons of Grand Rapids Michigan. There is no date on the box but it seems fairly old.

This is a small brass burr, called the "Ultimate Puzzle," made for Chadwick Miller and dated 1969. It came with a small black case with a question mark on the front.

In this aluminum burr, piece 824 is fixed to the base.

 

More Six-Piece Burrs

 

Kozy Kitajima's 6+6=Cube
This set of twelve burrs is called "6+6=Cube." It was designed by Kozy Kitajima. The pieces include: 1, 52, 103, 120, 188, 256, 911, 928, 992, 960, and 2x 1024. There is only one way to build two burrs at once. The twelve pieces can also be combined to form a cube.

 

Love's Dozen
88
    +----+    +----+    +----+----+
   /    /|   /    /|   /         /|
  +    + |  +----+ |  +         + |
 /    /  +--|    | +-/         /  +
+----+  /   |    |/ +----+----+   |
|    | +    +----+  |         |   |
|    |/             |         |   +
+    +----+----+----+         +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    
512
    +----+                   +----+
   /    /|                  /    /|
  +    + |                 +    + |
 /    /  +----+----+----+-/    /  +
+----+  /                +----+   |
|    | +    +----+       |    |   |
|    |/    /|   /        |    |   +
+    +----+ |  +----+----+    +  / 
|         | +--|              | +  
|         |/   |              |/   
+----+----+    +----+----+----+    
704
    +----+         +----+    +----+
   /    /|        /    /|   /    /|
  +    + |       +----+ |  +    + |
 /    /  +----+--|    | +-/    /  +
+----+  /        |    |/ +----+   |
|    | +         +    +  |    |   |
|    |/         /|   /   |    |   +
+    +----+----+ |  +----+    +  / 
|              | +--|         | +  
|              |/   |         |/   
+----+----+----+    +----+----+    
960
    +----+         +----+    +----+
   /    /|        /    /|   /    /|
  +    + |       +----+ |  +    + |
 /    /  +-------|    | +-/    /  +
+----+  /        |    |/ +----+   |
|    | +    +----+    +  |    |   |
|    |/    /|        /   |    |   +
+    +----+ |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
992
    +----+    +----+         +----+
   /    /|   /    /|        /    /|
  +    + |  +----+ |       +    + |
 /    /  +--|    | +----+-/    /  +
+----+  /   |    |/      +----+   |
|    | +    +    +----+  |    |   |
|    |/    /|        /   |    |   +
+    +----+ |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
1008
    +----+----+              +----+
   /         /|             /    /|
  +    +----+ |            +    + |
 /    /|    | +----+----+-/    /  +
+----+ |    |/           +----+   |
|    | +----+----+----+  |    |   |
|    |/    /|        /   |    |   +
+    +----+ |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    


This is Bruce Love's Dozen, (the version without the D's) purchased from Bill Cutler, and made from Maple by Jerry McFarland. This burr is special because it is the only burr at the highest level, 12. Unfortunately the solution is not unique - there are 89 ways to put these pieces together, and most of them don't achieve level 12. Note that there are no other level 12 burrs (for any length stick), and no level 11 burrs at all.

 

The Piston Burr
88
    +----+    +----+    +----+----+
   /    /|   /    /|   /         /|
  +    + |  +----+ |  +         + |
 /    /  +--|    | +-/         /  +
+----+  /   |    |/ +----+----+   |
|    | +    +----+  |         |   |
|    |/             |         |   +
+    +----+----+----+         +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    
512
    +----+                   +----+
   /    /|                  /    /|
  +    + |                 +    + |
 /    /  +----+----+----+-/    /  +
+----+  /                +----+   |
|    | +    +----+       |    |   |
|    |/    /|   /        |    |   +
+    +----+ |  +----+----+    +  / 
|         | +--|              | +  
|         |/   |              |/   
+----+----+    +----+----+----+    
768
    +----+                   +----+
   /    /|                  /    /|
  +    + |                 +    + |
 /    /  +----+----+----+-/    /  +
+----+  /                +----+   |
|    | +         +----+  |    |   |
|    |/         /|   /   |    |   +
+    +----+----+ |  +----+    +  / 
|              | +--|         | +  
|              |/   |         |/   
+----+----+----+    +----+----+    
922
    +----+    +----+----+    +----+
   /    /|   /         /|   /    /|
  +    + |  +         + |  +    + |
 /    /  +-/         /  +-/    /  +
+----+  / +----+----+  / +----+   |
|    | +  |         | +  |    |   |
|    |/   |         |/   |    |   +
+    +----+----+----+----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
1008
    +----+----+              +----+
   /         /|             /    /|
  +    +----+ |            +    + |
 /    /|    | +----+----+-/    /  +
+----+ |    |/           +----+   |
|    | +----+----+----+  |    |   |
|    |/    /|        /   |    |   +
+    +----+ |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
1008
    +----+----+              +----+
   /         /|             /    /|
  +    +----+ |            +    + |
 /    /|    | +----+----+-/    /  +
+----+ |    |/           +----+   |
|    | +----+----+----+  |    |   |
|    |/    /|        /   |    |   +
+    +----+ |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    


This is Peter Marineau's "Piston" burr, so named because of the large number of times pieces must be moved back and forth during the solution. This burr is special because it achieves the highest level possible for length-6 pieces, level 9 (i.e. it requires 9 moves to release the first piece), and the solution is unique - it has no other solutions at lower levels.

I made an example from Lego. I also bought a version made from six exotic woods, by Thomas Moeller. It is quite large - each piece measures 1.5" x 1.5" x 4.5".
Check Bill Cutler's site for availability.

 

Computer's Choice Unique 10
624
    +----+----+         +----+----+
   /         /|        /         /|
  +    +----+ |       +----+    + |
 /    /|    | +----+--|   /    /  +
+----+ |    |/        |  +----+   |
|    | +----+    +----+--|    |   |
|    |/         /|   /   |    |   +
+    +----+----+ |  +----+    +  / 
|              | +--|         | +  
|              |/   |         |/   
+----+----+----+    +----+----+    
702
    +----+         +----+    +----+
   /    /|        /    /|   /    /|
  +    + |  +----+----+ |  +    + |
 /    /  +-/    /|    | +-/    /  +
+----+  / +----+ |    |/ +----+   |
|    | +  |    | +    +  |    |   |
|    |/   |    | |   /   |    |   +
+    +----+    + |  +----+    +  / 
|              | +--|         | +  
|              |/   |         |/   
+----+----+----+    +----+----+    
768
    +----+                   +----+
   /    /|                  /    /|
  +    + |                 +    + |
 /    /  +----+----+----+-/    /  +
+----+  /                +----+   |
|    | +         +----+  |    |   |
|    |/         /|   /   |    |   +
+    +----+----+ |  +----+    +  / 
|              | +--|         | +  
|              |/   |         |/   
+----+----+----+    +----+----+    
883
    +----+              +----+----+
   /    /|             /         /|
  +    +----+    +----+         + |
 /         /|-+-/              /  +
+----+----+ |  +----+----+----+   |
|         | +--|              |   |
|         | |  |              |   +
+         + |  +----+         +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
1015
    +----+                   +----+
   /    /|                  /    /|
  +    +----+         +----+    + |
 /         /|-+----+-/         /  +
+----+----+ |       +----+----+   |
|         | +----+--|         |   |
|         | |       |         |   +
+         + |       +         +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
1024 Y Y [p2]
    +----+                   +----+
   /    /|                  /    /|
  +    + |                 +    + |
 /    /  +----+----+----+-/    /  +
+----+  /                +----+   |
|    | +    +----+----+  |    |   |
|    |/    /|        /   |    |   +
+    +----+ |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
The Y


This is Bill Cutler's Computer's Choice Unique 10 burr. I don't know who the craftsman is - I bought it as part of a group of hand-made puzzles. This burr is special because it is one of 18 burrs that have a unique level 10 solution, the highest level achievable for six-piece burrs with unique solutions. The pieces must be length-8, however, not length-6.

 

Tenyo Brother
463
    +----+----+----+         +----+
   /              /|        /    /|
  +         +----+ |       +    + |
 /         /|    | +----+-/    /  +
+----+----+ |    |/      +----+   |
|         | +    +       |    |   |
|         | |   /        |    |   +
+         + |  +----+----+    +  / 
|         | +--|              | +  
|         |/   |              |/   
+----+----+    +----+----+----+    
564
    +----+         +----+----+----+
   /    /|        /              /|
  +    + |       +              + |
 /    /  +----+-/              /  +
+----+  /      +----+----+----+   |
|    | +       |              |   |
|    |/        |              |   +
+    +----+----+----+         +  / 
|              | +--|         | +  
|              |/   |         |/   
+----+----+----+    +----+----+    
760
    +----+                   +----+
   /    /|                  /    /|
  +    + |            +----+    + |
 /    /  +----+----+-/         /  +
+----+  /           +----+----+   |
|    | +         +--|         |   |
|    |/         /|  |         |   +
+    +----+----+ |  +         +  / 
|              | +--|         | +  
|              |/   |         |/   
+----+----+----+    +----+----+    
909
    +----+----+----+----+    +----+
   /                   /|   /    /|
  +              +----+ |  +    + |
 /              /|    | +-/    /  +
+----+----+----+ |    |/ +----+   |
|              | +    +  |    |   |
|              |/    /   |    |   +
+         +----+    +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
927
    +----+    +----+----+    +----+
   /    /|   /         /|   /    /|
  +    +----+----+----+ |  +    + |
 /         /|         | +-/    /  +
+----+----+ |         |/ +----+   |
|         | +         +  |    |   |
|         | |        /   |    |   +
+         + |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
1016
    +----+                   +----+
   /    /|                  /    /|
  +    + |            +----+    + |
 /    /  +----+----+-/         /  +
+----+  /           +----+----+   |
|    | +    +----+--|         |   |
|    |/    /|       |         |   +
+    +----+ |       +         +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    

I bought this plastic burr in Japan. I believe it was made by Tenyo. It is number 4 in a "Family" of burrs - this one is called "Brother." This burr uses six general pieces: 463, 564, 760, 909, 927, 1016. It has no holes, and comes apart in one move into two 3-piece halves.
This might be #72 in Filipiak's list (c.f. Anthony S. Filipiak, 100 Puzzles - How to Make and Solve Them, 1942, p. 86).

 

G4
1 A A [p]
    +----+----+----+----+----+----+
   /                             /|
  +                             + |
 /                             /  +
+----+----+----+----+----+----+   |
|                             |   |
|                             |   +
+                             +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    
The Key
188 I M [p]
    +----+         +----+    +----+
   /    /|        /    /|   /    /|
  +    + |       +    + |  +    + |
 /    /  +----+-/    /  +-/    /  +
+----+  /      +----+  / +----+   |
|    | +       |    | +  |    |   |
|    |/        |    |/   |    |   +
+    +----+----+    +----+    +  / 
|                             | +  
|                             |/   
+----+----+----+----+----+----+    
The (Bottle) Opener
512
    +----+                   +----+
   /    /|                  /    /|
  +    + |                 +    + |
 /    /  +----+----+----+-/    /  +
+----+  /                +----+   |
|    | +    +----+       |    |   |
|    |/    /|   /        |    |   +
+    +----+ |  +----+----+    +  / 
|         | +--|              | +  
|         |/   |              |/   
+----+----+    +----+----+----+    
832
    +----+         +----+----+----+
   /    /|        /              /|
  +    + |       +----+----+    + |
 /    /  +----+--|        /    /  +
+----+  /        |       +----+   |
|    | +    +----+    +--|    |   |
|    |/    /|        /   |    |   +
+    +----+ |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
975 O Q [p]
    +----+----+----+         +----+
   /              /|        /    /|
  +         +----+ |       +    + |
 /         /|    | +----+-/    /  +
+----+----+ |    |/      +----+   |
|         | +    +----+  |    |   |
|         | |        /   |    |   +
+         + |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
Offsets
1024 Y Y [p2]
    +----+                   +----+
   /    /|                  /    /|
  +    + |                 +    + |
 /    /  +----+----+----+-/    /  +
+----+  /                +----+   |
|    | +    +----+----+  |    |   |
|    |/    /|        /   |    |   +
+    +----+ |       +----+    +  / 
|         | +----+--|         | +  
|         |/        |         |/   
+----+----+         +----+----+    
The Y

This burr's wooden length-12 pieces are stained a dark color. The burr comes in a box with a fitted slip-out cover. At some point I saw it referred to as "G4." The pieces used are: 1, 188, 512, 832, 975, 1024.

 

Miscellaneous
Here is a group of miscellaneous wooden burrs I've accumulated. Their pieces are shown below.

The light brown burr is perhaps the more difficult of this group, but we've seen it already - its pieces are the familiar "Rainbow" set:
52, 792/911, 824/975, 1024.
The white and two (identical) dark brown burrs all employ the familiar "ivory" piece set:
1, 256, 824/975, 928, 1024.

 

Burrs to Try


Obviously it would be nice to have a set of pieces all with consistent dimensions, in order to conveniently try different burr designs. In fact, there have been several sets produced, of varying completeness and quality. (I'll try to point out where you might find some, in the Sources section later.)

This section gives a list of burrs to try once you have a set (or can make your own pieces, for example from LiveCube or Lego). I've included solid and holey designs.

I made generic burr pieces (6x #1024, each requiring 14 cubes) from LiveCube. Then, with 20 extra pieces (here in yellow), one can build any of the possible burr pieces, and any set of six to try a particular burr.


This is a "Professor" burr set from the Yamanaka Kumiki Works in Japan. (I've also seen it called the "Professional Puzzle" set.) Its twelve length-8 pieces can be used to assemble at least four different traditional 6-piece burrs. The set includes only notchable pieces:

1, 18, 52, 154, 188, 256 x2, 824/975, 992, 1024 x2.

 

Wayne Daniel made this nice set of 42 of the notchable pieces which can be used to make 314 solid burrs, of Mahogany wood, with a Walnut box. Each piece is 0.75" square and 2.5" long, so his unit cube is 3/8 inches on an edge, and these are "length 6." The set includes a series of cards listing the six-tuples of each of the 314 burrs, and giving assembly hints by telling the adjacent pairings.

Unfortunately, I have found that certain holey burrs that are constructible from the notchable set, cannot be made to work using Daniel's set - his esthetic beveled treatment of the ends of the pieces, while fine for the 314 solid burrs, prevents certain necessary movements when trying the holey burrs. In particular, designs which use the "jutting jaw" technique as in the JVK 25.1 design, don't open far enough to allow the 3/8" cubie of a piece to pass through.

There are several sources that give the full list of all 314 solid burrs that can be produced with this set of 42 notchable pieces, including Slocum and Botermans' 1987 Puzzles Old and New; I have not attempted to give that full list here. Rather, I have tried to catalogue interesting puzzles I've run across and give their names or designers when I know them. The catalgoue below is ordered by piece number - with the six pieces sorted by number, lowest first. Mirror pair pieces are listed together.

I have color-coded the pieces per my guide tables above, to try to make it easier to see how the designs may be related. In addition...

Another classic puzzle book, 100 Puzzles - How to Make and Solve Them, written by Anthony S. Filipiak, was published in 1942 by A. S. Barnes and Company. In his book, Filipiak includes a section on the "Six Piece Burr Puzzle," beginning on page 79. He says that though he has over a thousand mechanical and manipulative puzzles in his collection, his favorite puzzle is the six piece burr. He gives diagrams for 38 burr pieces, and lists his "prize collection" of 73 burr puzzles using those pieces, "collected the world over by correspondence, travel, and research into ancient books of magic, tricks, games, and puzzles." He admits "no doubt there are a few more to be added." I have not reproduced all 73 designs here, but I highlight Filipiak designs like this.

Filipiak's notes seem to contain several errors: pieces #2 and #32 appear to be duplicates of what I call #18; #10 as drawn equals #463, but that interpretation results in several of Filipiak's designs having no solution - from its position in his list it might be a mistaken drawing of my #911, the complement to its neighbor #11 which is #792. Filipiak missed pieces #35 and #86, but there are only 3 uses of #35 among the 314 solid burrs, and only 2 of #86. He also missed the pair 856/943, but neither of those are used often, either. Several of the designs in his list of 73 puzzles, when I checked using Jurg's applet, have no solution - maybe the wrong pieces were listed, or as previously noted, the actual configuration of the pieces themselves are open to interpretation. Or, perhaps Filipiak himself hadn't bothered to actually construct all of the designs - but that seems unlikely given his enthusiasm. I cannot imagine that his editor could have checked the work!


I cannot claim to have "invented" any unique burr puzzles myself, but like others I have spent some time exploring the world that Cutler delimited. By analogy, the recent history of discovery related to this puzzle has been, to me, like the history of world exploration - at first, the "known world" was small and encompassed some well-traveled areas, beyond which lay either the "edge of the world" (for those who thought they had seen all the burrs and only "a few" remained to be found), or a "terra incognita" that stretched off into the hazy distance. Decades of exploration served to extend the frontiers of what was known, with some impressive voyages of exploration by intrepid souls using relatively primitive technology, but it was not until the computer age and Bill Cutler that a "satellite view" became available, delimiting the "globe" and showing its full extent - 35 billion assemblies. Most of that area is water - assemblies that cannot be constructed. Roughly 17% is land - the 5.95 billion constructible burrs. The "Old World" of the solid burrs stretches across 119,979 assemblies, and features many well-known cities and well-traveled routes. Cutler's satellite view has identified several impressive peaks in the larger world beyond, and much ground remains unexplored. Are explorers really "inventors?" Or, like the explorers of old, are they really more "discoverers?"

In particular I have been interested in finding high-level (holey) burrs that can be made with the notchable set, at length 6. Bruno Curfs has utilized computer analysis performed by Keiichiro Ishino, and makes several output files available at his site. Bruno mentions and discusses several burrs already, but there are a few which I'd like to flag as of interest as well:

Anyway, herewith my list, "collected the world over!"


  1. 1, 52, 188, 1024 x3
    - Wyatt #3, Filipiak #4
  2. 1, 52, 256, 928, 1024 x2
    - Wyatt #6, Filipiak #2 ; also see U.S. Patent 1425107 - Levinson 1922. Probably the pieces to the earliest known traditional six-piece burr, depicted in a 1733 book by Pablo Minguet y Irol (b. 1700 d. ca. 1775). Appeared as the "Small Devil's Hoof" in a 1785 catalogue.
  3. 1, 52, 256, 960/992, 1024
    - Filipiak #3 (corrected) - substituting 824 for 992, as given in Filipiak, won't work
  4. 1, 52, 256, 1024 x3
    - Wyatt #13, Filipiak #1
  5. 1, 52, 824, 992, 1024 x2
    - Filipiak #7 - the mirror of his #6. Professional Puzzle set #3
  6. 1, 52, 824, 1024 x3
    - Filipiak #5 - 1 solution; compare to Wyatt #11
  7. 1, 52, 960, 975, 1024 x2
    - Filipiak #6 - an improvement on Wyatt #11, substituting 960 for a 1024 and thereby eliminating the single void.
  8. 1, 52, 960/992, 888 or 1007, 1024
    - Filipiak #10 (use 1007), Filipiak #11 (use 888) - 2 solutions each.
  9. 1, 52, 975, 1024 x3
    - Wyatt #11
  10. 1, 103, 256, 928, 1024 x2
    - Wyatt #8, Filipiak #28
  11. 1, 103, 256, 960/992, 1024
    - Filipiak #37 - 3 solutions
  12. 1, 120, 188, 960/992, 1024
    - Filipiak #47 - 1 solution
  13. 1, 120, 871, 928, 1024 x2
    - Filipiak #48 - 1 solution
  14. 1, 128, 188, 512, 960/992
    - from Peter Kaldeway's site
  15. 1, 128, 512, 792, 928, 1024
    - Soviet Hedgehog
  16. 1, 154, 256 x2, 1024 x2
    - Wyatt #5, Filipiak #12, Professional Puzzle set #1. This one is very easy (BC #2). Any burr using 2x1024 is easier than most - adding 2x256 makes it somewhat trivial.
  17. 1, 154, 256, 888 or 1007, 1024 x2
    - Filipiak #22 (corrected, use 888 not 103 as listed), Filipiak #23 (use 1007)
  18. 1, 154, 871, 1024 x3
    - Wyatt #7, Filipiak #42
  19. 1, 188 x2, 256, 1024 x2
    - Filipiak #24
  20. 1, 188, 256 x2, 928, 1024
    - Filipiak #15
  21. 1, 188, 256 x2, 960/992
    - Filipiak #16
  22. 1, 188, 256 x2, 1024 x2
    - Wyatt #4 (also #12), Filipiak #14, can be made with the Professor set
  23. 1, 188, 256, 824, 992, 1024
    - Filipiak #27, Yamanaka Black set, can be made with the Professor set
  24. 1, 188, 256, 824, 1024 x2
    - Filipiak #25; compare to Wyatt #14; can be made with the Professor set
  25. 1, 188, 256, 960, 975, 1024
    - Filipiak #26; Described in Hoffmann's Puzzles Old and New Chapter III as No. XXXVI "The Nut (or Six-piece) Puzzle"; also sold as the "Burr Puzzle" by Toys From Times Past.
  26. 1, 188, 256, 975, 1024 x2
    - Wyatt #14, can be made with the Professor set
  27. 1, 188, 512, 576, 976, 1024
    - Dreveny Kriz II
  28. 1, 188, 512, 832, 975, 1024
    - Devil's Knot, G4
  29. 1, 188, 768, 824, 976, 1024
    - Puzzlemaster.ca calls this the Enigma; also known as "Notched Sticks." The pieces are kind of the "mirror image" of the Devil's Knot above - pick either the left or right of each of the three twins: 512/768, 832/976, and 975/824.
  30. 1, 188, 824/975, 1024 x2
    - The Yamato Block Puzzle, Filipiak #44, Professional Puzzle set #2. Easy. Also appeared as the "Locked Cross" from New Zealand. Also see U.S. Patent 1350039 - Senyk 1920.
  31. 1, 188, 871, 928, 1024 x2
    - Filipiak #43, Yamanaka Orange set
  32. 1, 188, 871, 960/992, 1024
    - Filipiak #46 - 3 solutions
  33. 1, 256 x3, 928 x2
    - The Diabolical Structure - possibly the easiest (BC #1). Filipiak #13
  34. 1, 256 x2, 792 or 911, 928, 1024
    - Filipiak #17 (use 911) and Filipiak #18 (use 792)
  35. 1, 256 x2, 792 or 911, 960/992
    - Filipiak #20 (use 911) and Filipiak #21 (use 792) - compare to Filipiak #17/18 and note how the 928+1024 pair replaces the 960/992 pair.
  36. 1, 256, 792, 928, 1007, 1024
    - vintage small wooden burr from England
  37. 1, 256, 824/975, 928, 1024
    - The Ivory Chinese Burr set; also Wyatt #1, Filipiak #29; also see U.S. Patent 1388710 - Hime 1921, for these pieces on a string.
  38. 1, 256, 824/975, 960/992
    - Filipiak #41 - 2 solutions
  39. 1, 256, 928, 960, 975, 1007
    - Filipiak #38; no soln for this set, but compare to the "Chinese Star"
  40. 1, 256, 888, 928, 960, 975
    - Saw this as the "Chinese Star."
  41. 1, 256, 888/1007, 928, 1024
    - Triple Cross
  42. 1, 464, 768, 800, 832, 1024
    - Brown's Burr - See U.S. Patent 1225760 - Brown 1917.
  43. 1, 824/975, 911, 1024 x2
    - Wyatt #2, Filipiak #49, if his #10 = 911
  44. 18 x2, 256 x2, 1024 x2
    - The 3rd easiest burr (BC #3).
  45. 18 x2, 512/768, 1015, 1024
    - Filipiak #63 - 1 solution
  46. 18, 35, 871, 1024 x3
    - one of only 3 uses of piece #35 among the 314 solid burrs.
  47. 18, 52, 256 x2, 928, 1024
    - 4 apparent assemblies but only 1 solution. Not too tough.
  48. 18, 52, 256, 824, 992, 1024
    - Professional Puzzle set #4
  49. 18, 52, 256, 911, 1024 x2
    - Wyatt #10, Filipiak #66, if his #10 = 911
  50. 18, 52, 871, 928, 1024 x2
    - Yamanaka Green set
  51. 18, 86, 871, 960/992, 1024
    - one of only two uses of piece #86 among the 314 solid burrs.
  52. 35, 52, 871, 928, 1024 x2
    - the second of only 3 uses of piece #35 among the 314 solid burrs.
  53. 35, 52, 871, 960/992, 1024
    - the third of only 3 uses of piece #35 among the 314 solid burrs, this set goes together 3 ways.
  54. 35, 359, 960/992, 975, 1024
    - EFNOQY discussed by Bruno Curfs
  55. 35, 975, 992 x2, 1024 x2
    - EOOQYY - Simple Lock
  56. 52 x2, 103, 871, 1024 x2
    - Wyatt #9, Filipiak #64 - NOTE - this set doesn't work - it has too many interior cubes. Why did they both include it?
  57. 52 x2, 256 x2, 928 x2
    - Another very easy burr - BC #4
  58. 52 x2, 256, 911, 928, 1024
    - Yamanaka Yellow set
  59. 52, 86, 871, 928, 960/992
    - the second of only two uses of piece #86 among the 314 solid burrs.
  60. 52, 88, 768, 888, 992, 1024
    - Bill Cutler's BB31-10-40 - the least un-notchable 1-hole level 3
  61. 52, 103, 871, 928, 960/992
    - LNOPST - 3 assemblies, 1 solution; Bruno Curfs rates this 5th hardest among the solid notchables
  62. 52, 154, 256 x2, 911, 1024
    - Filipiak #65 - this has no solution regardless of whether his #10 is 463 or 911; compare to Wyatt #15 below, where instead of 256x2 there is 1024x2. It seems like there would be space for the 256, but the puzzle cannot be assembled then. Another mistake in Filipiak?
  63. 52, 154, 256, 911, 1024 x2
    - Wyatt #15 - 3 solutions
  64. 52, 256, 888/1007, 1024 x2
    - Jurg von Kanel's Burr in a Cube - assemble this inside a cubic cage.
  65. 52, 615, 792, 960/992, 975
    - Bill Cutler's No. 305. A nice 3x3 slide. gamesandpuzzles.co.uk has it.
  66. 52, 615, 792, 871, 960/992, 975
    - Gemani's Double Bill (combines Cutler's 305 and 306)
  67. 52, 615, 871, 960/992, 975
    - Bill Cutler's No. 306. - Cutler, Coffin, and Curfs say this may be the most difficult notchable solid burr.
  68. 52, 615, 856, 928, 960, 975
    - 52+928 (DV or PL) makes a 2-piece key
  69. 52, 792/911, 824/975, 1024
    - The 6-way (Rainbow). 8 apparent assemblies, 6 solutions. An old one sold as "The Zoozzler."
  70. 55, 508, 768, 812, 960, 1023
    - Derwin Brown's Unique Level 6
  71. 56, 94, 156, 704, 1008, 1024
    - Stewart Coffin's Triple Slide
  72. 63, 480, 512, 766, 896, 1012
    - Curfs BC UL7000
  73. 72, 112, 448, 511, 990, 1024
    - Stewart Coffin's No. 40 Interrupted Slide (1979) - one of the "Fearsome Four"
  74. 86, 160, 224, 992, 957, 1016
    - JVK #25.2 derivation
  75. 86, 256, 911, 992, 928, 1024
    - JVK #25.2 - a level 3 design which uses piece #86.
  76. 88, 160, 512/768, 992, 1008
    - Edward Hordern's modification to Peter Marineau's Piston Burr - 13 solutions, one at level 10
  77. 88, 512, 704, 960/992, 1008
    - Bruce Love's Dozen. The only burr at the highest level, 12. There are 89 ways to put it together, but most of them don't achieve level 12.
  78. 88, 512/768, 922, 1008 x2
    - Peter Marineau's Piston Burr - The highest level, 9, with a unique solution.
  79. 103, 160, 224, 824, 928, 1024
    - Millable 5.4
  80. 103, 188, 256, 928, 975, 1024
    - Jurg von Kanel's jvk25.1 - Note: the notch in piece #256 (X) in my copy of the Wayne Daniel burr set is too short and prevents piece #975 (Q) from being removed, so this one cannot be constructed using the set.
  81. 103, 256 x2, 824, 928, 960
    - LNRSXX - unique level-5 solution, discussed by Bruno Curfs
  82. 103, 256 x2, 928 x2, 960
    - LLNSXX - unique level-5 solution, discussed by Bruno Curfs
  83. 103, 256, 412, 824, 928, 1024
    - Jurg von Kanel's favorite notchable burr
  84. 103, 508 x2, 824, 928, 1024
    - David Winkler's favorite level 5.4 Millable burr
  85. 103, 760, 960/992, 996, 1024
    - Bill's Baffling Burr; Gemani's Deadlock - 5 moves to release the 1st piece. One of the "Fearsome Four."
  86. 109, 188, 736, 928, 1008, 1024
    - Bruno Curfs' BC L6000 - nice, 6 moves to free the 1st piece
  87. 120, 154 x2, 256, 1024 x2
    - Ishino's Notchable 5-Moves 2-Hole - (a set of 42 does not have 2x 154) Note: again, the problem with #256 in the Wayne Daniel set prevents this construction.
  88. 120, 154, 188, 928, 1024 x2
    - KLMUYY can be made with the set of 42
  89. 120, 154, 256 x2, 960/992
    - KNOUXX - only multiple level-5 solutions
  90. 120, 160, 256, 512, 880, 960
    - Philippe Dubois/Gaby Games - 6 moves to release the 1st piece. One of the "Fearsome Four."
  91. 120, 188, 670, 928, 992, 1024
    - David Winkler's favorite 5.4
  92. 120, 188, 792/911, 975, 1024
    - Ishino's Notchable 2-Moves 1-Hole #3
  93. 120, 188, 871, 928 x2, 1024
    - Tumult - try to find the level 7 solution.
  94. 120, 792/911, 824/975, 992
    - Bill Cutler's Notchable 1-Hole Level 2 - uses only notchable pieces and has only one void - 4 solutions, one at level 2.
  95. 126, 615, 820, 856, 928, 1024
    - Stewart Coffin's No. 36 Improved Burr (1979) - One of the "Fearsome Four."
  96. 144, 495, 702, 975, 990, 1024
    - Abad's Level 5.7 Improved Burr
  97. 154, 256 x4, 1024
    - U.S. Patent 1542148 - Kramariuk 1925.
  98. 158, 768, 824, 863, 992, 1012
    - Curfs BC UL5000
  99. 160, 188, 412, 751, 960, 1024
    - Ishino's Millable Unique 5.4.2-Moves 4-Hole
  100. 160, 499, 512/768, 926, 1015
    - Bill Cutler's Computer's Choice 5-Hole
  101. 160, 508, 736, 742, 768, 1015
    - Abad's Level 9 Burr
  102. 188, 256, 615, 975, 928, 1024
    - GLMQXY - this one works like JVK 25.1
  103. 192, 736, 768, 976, 1007, 1008
    - Peter Roesler's #G
  104. 256 x5, 992
    - David Winkler's Level 3 - use either of the Fingers 960/992, or 928.
  105. 256, 551, 960/992, 992, 928
    - Bill Cutler's L5 Notchable - one of 139 designs using only notchable length-6 pieces and having a unique solution
  106. 256, 792/911, 943, 960,