These Schnorr Safety Washers are in the form of a disc spring which is serrated on both sides and of trapezoidal cross section. Their internal diameters are matched to the thread diameter of screws/bolts. The outer diameter of the washer is matched to the head diameter of pan-head and hexagon socket head cap screws/bolts. As a result, the Safety Washer can be used with practically any screw and bolt type, including those with recessed heads (cannot be used with countersunk screws/bolts). The ingenious form of the Schnorr Safety Washer combines the advantages of security through friction and mechanical locking.Advantages:The shape of the cross section ensures the locking effect is at the outside diameter which ensures the greatest resistance to loosening.High resistance to vibration due to positive locking of the serrations.The closed ring form results in a high degree of pretensioning, i.e. an excellent frictional connection.Concentric application of force eliminates bending in the bol