Hinge #3, standard 18 gauge, plain steel. Used between sections 3 and 4 on the door. The #3 has a larger offset than the #1 and #2 so the roller stays in the right position as the door moves through the curve of the track. If your old hinge is bent, cracked, or worn out, replace it and match the number stamped on the original hinge before ordering. The 18 gauge steel is a standard residential option for everyday garage door use.