The intended application governs: hinges designed and marketed for installation in buildings (doors, windows, shutters) go under 830241, while those designed for furniture (cabinet doors, chest lids) go under 830242. When a hinge is genuinely dual-use, the importer should document the primary intended application and may seek a CBP binding ruling.

Castors have their own dedicated subheading (830220) regardless of what they are attached to. The furniture fittings subheading (830242) covers mountings and fittings other than castors, so office-chair castors remain under 830220.