Flange nuts have a wide flange at one end that acts as an integrated, non-spinning washer. This serves to distribute the pressure of the nut over the part being secured, reducing the chance of damage to the part and making it less likely to loosen as a result of an uneven fastening surface. The flange is also serrated to provide a locking action. The serrations are angled such that they keep the nut from rotating in the direction that would loosen the nut. Because of the serrations they cannot be used with a washer or on surfaces that must not be scratched. The serrations help in preventing the vibration of the nut from moving the fastener, thus maintaining the holding power of nut.There are a variety of serrated flange nut types in different grade and meet the standards of both DIN and ISO.