The Carton Furniture series, designed in 1965, is a stool that has enough weight capacity to be used as a chair, but is lightweight enough that children can use it as building blocks. Made from a recyclable material called cardboard, its robustness is enhanced through a perfect assembly structure. At the time of its release, it was talked about as ``four stools can support the weight of an elephant.'' It can be assembled without using adhesives, just by mountain folding, valley folding, and fitting. It is easy to disassemble and can be folded and stored compactly. It is widely used in public facilities and workshops, and since you can also draw on the surface, it is also used in nursery schools and kindergartens that emphasize free thinking.