A serrated washer is also known as Vibration Proof Washers. Serrated lock washers increase the friction between the bolt head/nut and the mating surface.They are available in various sizes to fit bolts or screws.Serrated Washers are fitted internally to the equipment before a lock nut and act as an anti-vibration device to prevent the Cable Gland or accessory from inadvertently loosening in service.Often used on cable gland entry threads, these washers come in stainless steel as standard but can be made in a number of materials upon Customer request.