Testing & Certification Lug-All Permatex Cabinets Scoop Drawers Polyboxes. Washers provide a smooth bearing surface and are used under the head of a bolt and / or a nut. Lock Washer Specifications. Engineering Videos aluminum. PLEASE NOTE: COVID-19 We are open and continuing operations as a designated Essential Supplier. Advertising Item #136835 Model #880401 Wedges on the inside lock the two pieces together, and serrations on the exterior grip surfaces to resist loosening from high vibration and shifting. Helical Split spring lock washers are available in four series: Regular, heavy, extra duty and hi-collar as given below. When compressed by tightening the nut, the washer bites into the