SHS RSH,A Hollow Structural Section, or HSS, is a type of metal with a hollow tubular section. These sections can be circular (CHS), square (SHS) or rectangular (RHS).
Hollow Structural Sections, especially RHS steel is commonly used in welded steel frames while SHS and CHS are more often used in columns. Hollow Steel Sections are also commonly used as beams. The flat square surfaces of RHS has the ability to ease construction, and they are sometimes preferred for architectural aesthetics in exposed structures, but circular Hollow Structural Sections are becoming more popular in exposed structures for the same reasons.