A barrel nut is a specialized nut that is commonly used in aerospace applications. It is used to bolt thin sheet metal parts to larger, often billet or forged, parts. The barrel nut is a round slug, or formed sheet metal part with threads perpendicular to the length of the nut. The nut sits in a hole inside the forging and a standard machine screw is threaded into the barrel nut from outside the sheet metal. They are preferred over a standard nut and bolt, because they do not require a flange to be machined or forged onto the receiving part, thus reducing weight.[1]