TJ (or TJI): Manufactured truss joints resembling the letter I that are used as floor joists and rafters. I-joists include two key parts: flanges and webs. The flange may be made of laminated veneer lumber or dimensional lumber, usually formed into a width of 1-1/2 inches. The web is commonly made of plywood or oriented strand board (OSB). Large holes can be cut in the web to accommodate ductwork and plumbing waste lines. I-joists are available in lengths up to 60 inches long.