The traditional 6-Piece Burr Puzzle is perhaps the most well known and legendary of all the Burr puzzles, and maybe even all interlocking puzzles in general. It’s a classic! The origin of the OG burr puzzle is unclear, but experts have traced it back to the beginning of the 19th century in Germany. Two types of burrs have emerged over the years; the first type contains no internal gaps (solid all the way through) and has a uniform bar as the “key”. The second type does contain gaps within the interior of the puzzle body, creating more of a challenge to visualizing the pattern of configuration. Our classic 6-Piece Burr is solid and contains three sets of rod pairs; all pieces need to intersect to form the classic burr shape.