The determining factor is whether the semi-fabricated form has been prepared specifically for use in a structure — for example, cut to length, drilled, punched, or otherwise worked to fit a defined structural application. Generic mill-length plate or rod not yet worked for a specific structural purpose is generally classified under primary aluminum mill-product headings. Once the material is dimensioned and prepared for a specific structural assembly, it may properly fall here, though the line is fact-specific and often requires a CBP ruling.

Aluminum extrusion antidumping/CVD orders cover extruded aluminum shapes from certain countries, and structural components made from extrusions may be within scope even when assembled into larger systems. Importers should review the order's 'finished goods kit' exclusion language and any published scope rulings addressing structural assemblies. Where uncertainty exists, a formal scope ruling request to the Department of Commerce is the most reliable way to establish a defensible position before importation.