Nut

Finish: HDG to meet ASTM A153

Size: 1/2”,5/8”, 3/4”, 7/8”,1” square and Hex

Feature:Used as a locking nut on the back of nuts. When concave side of locknut bears down top of square or hex nut, the arch is flattened, deflecting the nut threads from their true helix and causing them to firmly grip the bolt threads.
Hubbell: 3510, 3511, 3512, 3513,