Hollow steel structure is made up of Hollow Structural Sections (HSS);is a type of metal profile with a hollow cross section. It is produced in round, square and rectangular shapes and a broad range of sizes. They are high-strength welded steel tubing to form the structural frame to support the roofing material.Rectangular sections, are commonly used in welded steel frames. Round sections are for columns. They also have excellent resistance to torsion.HSS can also be used as beams, although wide flange or I-beam shapes are in many cases a more efficient structural shape for this application. HSS has superior resistance to lateral torsional buckling.The flat square surfaces of rectangular HSS can ease construction, and they are sometimes preferred for architectural aesthetics in exposed structure.