The steel contractor takes the raw steel from the supplier and turns it into beams, posts, and columns. For example, a simple “I” beam is made by welding together two flanges and a web. The original three pieces are simple flat stock. Likewise a simple steel tube post, first has to have a top and bottom plate welded to it before it’s delivered and installed. Make sense? Different companies do different things. The farmer grows the wheat, the grain company processes it, and the baker turns it into bread.