Nord-LockRis a pair of washers with a wedge-locking action meeting DIN 25201 which is a unique method using tension instead of friction. The rise of the cams between the Nord-LockR washers is greater than the pitch of the bolt. In addition, there are radial teeth on the opposite side. The washers are installed in pairs, cam face to cam face.
The Nord-LockR washer is locked in place, allowing movement only across the face of the cams. The tension created makes the bolt/nut self-locking so it cannot move.

When the bolt and/or nut is tightened the teeth grip and seat the mating surfaces. The Nord-Lock® washer is locked in place, allowing movement only across the face of the cams. Any attempt from the bolt/nut to rotate loose is blocked by the wedge effect of the cams.

Here you see what happens when a bolt is untightened with a wrench. The pair of washers expand more than the corresponding pitch of the thread allows the bolt/nut to rise.