Chinese Cross Puzzle "

This ancient Chinese puzzle is known as the

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By Stewart T. Coffin

Chapter 5 - The Six-Piece Burr

Puzzles consisting of interlocking assemblies of notched sticks are often referred to as burr puzzles, probably from being pointed or spur-like in assembled appearance. By far the most familiar of all burr puzzles, and probably of three-dimensional puzzles in general, is the so-called six-piece burr.

The standard six-piece burr consists of six notched square sticks of arbitrary equal length not less than three times their width, arranged symmetrically in three mutually perpendicular intersecting pairs. If the square cross-section of the sticks has a dimension of two units, then all notches are one unit deep and one unit wide or some exact multiple. To put it another way, all notches can be regarded as being made by removal of discrete cubic units, or to put it still another way, all pieces can be regarded as being built of cubic units. All of the notches are made within the region of intersection with the other sticks, so that when the puzzle is assembled no notches show and it has apparent symmetry

see also A Computer Analysis of All 6-Piece Burrs By Bill Cutler