ROKR Locomotive Mechanical Wooden Gear 3D Puzzle Kit About this item LASER-CUT MODEL KIT - Unique Mechanical 3D Puzzle,laser-cut ply wood material,no tonxic,environmental friendly,smooth wooden board.All pieces are pre-cut,no glue needed.The interlocking mechanisms are pretty ingenious. SELF PROPELLED WOODEN PUZZLE - Wooden mechanical gears toy is operated by a hand wound spring,no battery,no other power need,self propelled but you need to use a little wax and the tool provided to make it move smoothly. DETAILED ENGLISH INSTRUCTIONS - Follow the user manual provided in the brain teaser DIY puzzle,and you will be able to install it.Making this mechanical model toy requires not only attentiveness but also patience.Feel the pride of assembling this entire IQ toy set-up with your very own hands.