Hinge #1, 14 gauge heavy duty, plain steel. Goes between section 1 and section 2 on the door. The #1 has the smallest offset of all the numbered hinges because the bottom of the door stays mostly vertical during operation. When yours is bent or the holes are elongated from wear, swap it out. Check the stamped number on your old hinge to confirm it is a #1. Heavy duty 14 gauge is thicker than the standard residential hinges so it holds up better on heavier doors or doors that get a lot of use.