Since 1939, the Steel Deck Institute has provided uniform industry standards for the engineering, design, manufacture, and field usage of steel decks. The SDI is concerned with cold-formed steel products, with various configurations distinctive to individual manufacturers, used to support finished roofing materials or to serve as a permanent form and/or positive reinforcement for concrete floor slabs.   Members of the Institute are manufacturers of steel floor and roof decks. Associate members are manufacturers of products used in the production or erection of steel decks.   The Institute is managed by an executive director who supervises the programs developed through the combined efforts of the total membership. Continuing SDI functions include preparation, review, and distribution of literature, referral of inquiries to appropriate sources, coordination of research and testing, and liaison with other construction industry associations on matters of common interest.