steel building materials, namely, steel studs, steel beams in the nature of studs, prefabricated steel wall panels, rafters, steel beams, steel framing accessories, namely, steel framing studs, steel wall assemblies comprised of steel wall studs, steel stud brackets, and steel wall panels, steel roof assemblies comprised of steel roof beams and steel roofing brackets, steel lintels, steel bridging, steel structural joint connectors, steel purlins