Aluminium; aluminium and its alloys; beams of common metal for scaffolding; common metals; common metals and their alloys; fasteners of metal for scaffolds; fittings of metal for building, namely, brackets, joints, couplers, and frames; ladders of metal; materials of metal for scaffolds; metal flooring; metal ladders; metal scaffolding; railings of metal; scaffolding of metal; scaffolding towers of metal