A hex nut is designed to be installed on the end of a hex bolt or other precision screw, and typically holds a fastener in place when used next to an unthreaded hole. Material: Carbon Steel, 201 Stainless Steel, 304 Stainless Steel, 316 Stainless Steel, Brass. Style: US Thread, Metric Thread, Imperial Thread UNC/UFC Size. Used to connect metal and wood components. Hex Nuts are intended for use with screws and bolts to provide secure fixings in unthreaded holes. Designed for basic fastening requirements which are often suitable for most applications.