Size (in) according to customer Grade SS 304 Hinge Type Butt Hinge Finish Polished Features Heavy Duty Corner Type Square Application Door A door hinge is the hardware component that lets a door swing open or closed while remaining attached to the door frame. A “Stainless Steel (SS) Door Hinge” is simply a hinge made from stainless steel instead of ordinary mild steel or other metals — which gives it important advantages.