Structures (excluding Prefabricated Buildings Of Heading 9406) And Parts Of Structures (for Example, Bridges And Bridge-sections, Lock-gates, Towers, Lattice Masts, Roofs, Roofing Frameworks, Doors And Windows And Their Frames And Thresholds For Doors, Shutters, Balustrades, Pillars And Columns), Of Iron Or Steel; Plates, Rods, Angles, Shapes, Sections, Tubes And The Like, Prepared For Use In Structures Of Iron Or Steel