StillCool 3D Jigsaw Puzzles Wooden Classic Cube Genius Puzzle and Brain Teasers, Set of 6 Old China Kongming Luban Jigsaw Lock Educational Toy Gift for Kids and Adults The lock may look simple, but it contains lots of mysteries, to challenge your mind and test your nerve. Easy to take apart and difficult to reassemble. Made of wood, 6 pieces include. Difficulty: Medium to Very Hard. Maintenance: Handle with care, avoid desiccation, being washed.