Cooks think of this as a way to tie up a turkey. In construction, it plays a different kind of supporting role. A truss is a prefabricated, triangular structure, typically made of wood connected to metal plates. It can be used to provide a framework for a floor or roof. Trusses use less wood than traditional rafters and joists built on-site from dimensional lumber. The greenest products are made with wood certified by the Forest Stewardship Council (FSC).