Nord lock is a certified fastening system utilizing the wedge-effect that makes the mating bolt self locking. It prevents the loosening of the bolt due to vibration or dynamic loads. These are more usually used on industrial, oil field sectors and some other critical applications. Nord lock washers are installed in pairs and should not be installed as an individual washer. It has also got an added advantage of consistent reusability without the loss of quality. Please make sure to re-install the Nord-Lock washers correctly.Also available in stainless steel and carbon steel material.