Section 15 Base metals and articles of base metal 73 Articles of iron or steel 73 08 Structures (excluding prefabricated buildings of heading 94.06) and parts of structures (for example, bridges and bridge-sections, lock-gates, towers, lattice masts, roofs, roofing frame-works, doors and windows and their frames and thresholds for doors, Commodity Code Description 73 08 10 Bridges and bridge-sections 73 08 20 Towers and lattice masts 73 08 30 Doors, windows and their frames and thresholds for doors 73 08 40 Equipment for scaffolding,shuttering, propping or pitpropping 73 08 90 Other