The steel machine screw hex nut has a zinc-plated finish and meets American Society of Mechanical Engineers ASME B18.6.3 specifications. Designed for use with machine screws, the nut has a flat top with a large bearing surface and chamfered corners. 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. Steel is often used in applications where strength is the primary consideration. The zinc plating offers corrosion resistance and has a reflective appearance.

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.