Section 15 Base metals and articles of base metal 73 Articles of iron or steel 73 08 Iron/steel structures and parts thereof; plates, rods... therefor 73 08 20 Prefabricated modular type joined by shear connectors 73 08 20 21 Prefabricated modular type joined by shear connectors Commodity Code Description 73 08 20 21 00 Prefabricated modular type joined by shear connectors