NORD-LOCK safety washers use wedge-locking to securely lock critical bolted joints. By the cam pitch of the washers being greater than the thread pitch, a wedge-locking effect is created. The pair of washers expands more than corresponds to the thread pitch of the screw, thereby increasing the clamping force in the joint. The bolted joint becomes self-locking and provides maximum safety for bolted joints exposed to vibration and dynamic loads. The trays are delivered in pairs pre-assembled for quick and easy assembly.