6 Common metals, unwrought and semi-wrought, and their alloys; building materials of metal; metal panels and metal panels and fittings thereof; slabs, laths, plates, sheets and plates of metal, beams, rungs, panels, cylinder, corner brackets and tubes of metal; metal tracks for rail vehicles; steel, unwrought or semi-wrought; rolled steel; structural elements, of steel; framework of metal for building; linings of metal for building; metal constructions with double skinned heat insulated facade; roof coverings of metal