Thin Nut

12 NUT = JAM NUT. Named differently, but basically the same. Usually, two of these nuts are used together as a 'locking nut'. Very effective, and used before the advent of Nylocks etc. In this example, the half nut is also oversized 'across the flats', so could also be considered a 'wide nut'. WIDE NUT. These are made for special applications, and are usually made from hex bar the next largest size.