Washers provide a smooth bearing surface and are used under the head of a bolt and / or a nut. Flat washers are covered under the DIN 125 A / DIN 125 B standards. These washers are unhardened and intended for general use

Split lock washers provide greater bolt tensioning for tighter assemblies and provide protection against loosening resulting from vibration. Lock washers can be used with a standard washer to provide uniform bearing surface. These washers are unhardened and intended for general use.