Burr puzzle

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A burr puzzle in unsolved form

The same puzzle, solved

Burr puzzles are interlocking puzzles known in Europe and Asia since at least the 18th century. Traditionally they are made from wood, but some modern versions use plastic (for cheapness) while collector's quality ones may be made from brass (for durability). The wooden burr puzzles are usually precision-made for tight fit and require special wood so that the pieces do not change shape too much in changing temperature and humidity.

The burr puzzle gets its name from the most traditional shape for the finished puzzle, a symmetrical arrangement of intersecting cuboids thought to resemble a seed burr, but similar puzzles can have other forms when assembled, ranging from a ball to the shape of a human figure, a ship, a bird or a free-form starlike contraption.

The mathematical properties of burr puzzles have been studied by Bill Cutler.