“I was thinking of creating a folding chair, where the dynamics of opening and closing of the rotating parts could be solved with a single joint, and also thinking of the seat and back stamped from a transparent plastic sheet on a structure of very thin steel tubes.” Giancarlo Piretti had in mind a theorem, which he intended to demonstrate: the joint as the fulcrum of action declares or negates the composition of the seat, and in action alternately achieves both forms, open for use, closed for storage.