A split beam nut, also known as a split hex nut[1] or slotted beam nut,[2] is a locknut with slots cut in the top that separate the outside end into two[3] or more sections that are bent slightly inward, making the thread diameter undersized in the slotted portion. As the nut is threaded on, these sections are forced back out to their original position and increase the friction between the nut and the fastener, creating the locking action.