Stover-Type Lock Nuts
Stover®-type lock nut are referred to generically as prevailing torque lock nuts and are one piece and have a locking mechanism that’s built into the cone by distorting the threads. As you put it on, it starts to lock by creating frictional interference between the threads of the mating components. When fastening a prevailing torque lock nut, there is a resistance to rotation during both assembly and disassembly requiring them to be wrenched; you can't do it by hand. The locking action, created by distortion of their top threads, is said to resist loosening caused by shock, vibration and other dynamic forces.
There is also a collar type version of this nut, usually only seen in larger diameters. The locking mechanism is part of the collar. These types of nuts can also be made out of flange nuts giving a lock at the top and the underside of the nut. Some flange nuts have both the prevailing torque and the nylon insert and the serrations.