Nordlock
Nord-lock washers have cams on one side with a greater rise than the pitch of the bolt. In addition, they have radial teeth on the opposite side. The washers are installed in pairs, cam face to cam face.

When the bolt and/or nut is tightened, the teeth grip and seat the mating surfaces. The teeth lock the washers in place, allowing movement only across the face of the cams. The tension created makes the bolt/nut self-locking.

Advantages:
1) Achieves maximum safety when locking fasteners
2) Resist loosening caused by vibration
3) Ease of assembly and disassembly
4) Locking function is not lost by lubrication
5) Positive locking at low or high preload levels
6) Same temperature characteristics as std. bolt/nut or corresponding quality
7) Minimum surface marring or scratching
8) Reusable