The grade C steel hex nut has a self-locking top-lock design and a zinc yellow-chromate plating. It has six flat sides that a wrench can grip to turn from the side, enabling use when there is no space above the nut. The self-locking top threads are deformed to help prevent loosening when the nut is threaded to another component. Grade C steel, composed of carbon steel, is often used in applications where strength is the primary consideration and is harder than Grade A steel. The zinc yellow-chromate plating offers good corrosion resistance.

Nuts are internally threaded fasteners that are used with bolts and threaded rods and studs to connect components. Several different nut styles fit a variety of application and installation requirements. Some styles, such as hex nuts, acorn nuts, flange nuts, and coupling nuts, must be tightened with a tool. Others, such as eye nuts, thumb nuts, and wing nuts, can be tightened by hand. Some nuts have a self-locking mechanism, such as a nylon patch or distorted threads, that makes them suitable for applications with a high amount of vibration.