The class 4 steel hex jam nut has a zinc-plated finish and meets Deutsches Institut fr Normung DIN 439B specifications. Also called a thin nut, it is thinner than a standard hex nut for use in tight areas and is often used with another jam nut to help prevent loosening. 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. Class 4 steel is often used in applications where toughness 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.