The Grandfather Burr Puzzle - 18 piece burr puzzle
This Grandfather Burr Puzzle is one of the hardest interlocking puzzles in our collection. The Grandfather Burr Puzzle was designed by W. L. van der Poel, a Dutch computer scientist that used to design and create puzzles as his hobby. The Grandfather Burr Puzzle has 18 pieces, all with notches. The puzzle's design makes it extremely difficult because there are "holes" in the interior of the puzzle body, unlike most other regular burr puzzles that have no holes.