Midwest Fasteners Self-Locking Washers are used in conjunction with Midwest Fasteners weld pins, insul-anchors and lacing anchors to fasten insulation in place. Simply press the self-locking washer onto the pin up to the insulation until the desired position is reached. Then clip off, (or bend over) the remaining portion of pin for a permanent attachment. Round self-locking washers are available as a matter of design or application preference. The domed, multi-lanced hole design provides for ease of locating washer on pin and positive locking. Washers are manufactured with a beveled edge to prevent the washer from cutting into the insulation facing.