Readily erectable steel buildings, knockdown steel buildings, prefabricated steel buildings, girders, girder-posts, beams and columns sills, bridging, joists, purlins, doors, door frames, windows, window frames, flashing, furring, studs, gutters, headers, rafters, ribs, bulkheads, angle sections, channels, L shapes, C sections, box sections made of base metal, ornamental metal trim, stud plates, stud caps, ridge caps, sheathing, roofing, siding, trimmers, splice plates, tie rods and frame work connecting brackets being manufactured articles of steel in this Class,