The Interlocking Ladder Puzzle is based on the "Japanese Crystal Puzzle" originally designed in Japan circa the 19th century. This stunningly ornate and intriguing device is one of the most challenging units in our entire interlocking puzzle collection. Symmetrical, multifaceted, and celestial, the structure is made out of 51 non-identical, interlocking bars. Each piece is precisely cut so they interlock perfectly to make a solid structure. Similar to many construction/interlocking puzzles, the key to unraveling the Ladder puzzle is to turn just one key piece. Afterward, there are precise steps that must be followed to unlock the rest of the puzzle. After the pieces have come apart, are you up to the task of rebuilding it? This high-level, extremely difficult puzzle is perfect for serious puzzlers with heaps of extra time on their hands. The Ladder Puzzle is perfect for building focus, patience, and spatial reasoning. Once you’ve solved the puzzle it makes a beautiful art piece to display on a bookshelf or coffee table! Warning: Choking Hazard – Small Parts. Not for Children Under 3 Years.