Steel Joist are open-web lightweight steel trusses composed of parallel chords and a triangular web system, proportional to the span between support points. They provide direct support for roof or floor decks and transfer loads applied on the deck to the beams and columns of the structural framing. The joist is the primary structural member, usually supported by columns, but can also be supported by other structural elements. Special profile steel joists are available in a variety of profiles.