The manufacturing process is the key classifier: cast and rolled glass is formed by pouring molten glass onto a surface or passing it through rollers, often producing a textured or patterned surface. Drawn or blown glass is formed by mechanically drawing or blowing, typically yielding a smoother, more uniform sheet. CBP may request production process documentation or technical specifications if the method is not evident from the product's physical characteristics.

Trade remedy coverage in the glass sector can be product- and origin-specific. Importers should check the USITC and Commerce Department databases for any active antidumping or countervailing duty orders covering flat glass products from specific countries before finalizing sourcing decisions, as the scope of existing orders can sometimes extend to unworked sheet forms.