In traditional Sashimono furniture-making, craftsmen fit pieces of wood together without nails and/or use a ruler in making the item. Artisans assemble each piece using concave and convex parts called "tenons" in hidden areas to hold the structure together and provide strength. Although the furniture may appear to be delicate as a result of the thin boards used, it is in fact extremely sturdy due to the use of traditional joinery techniques.