Aluminium Washers Copper Washers Locking Washers Plain Steel Washers Spring Washers Thrust Washers Washer Plates Plastic Washers Clear Washers Nut & Bolt Washers Flat Washers. The main purpose of a washer is to distribute the load under the bolt head and nut face. Plain washers are best avoided if possible and certainly, a plain washer should not be used with a 'lock' washer. It would partly decrease the effect of the locking action. Many 'lock' washers have been shown to be ineffective in resisting loosening. One problem that can occur with washers is that they can move when being tightened so that the washer can rotate with the nut or bolt head rather than remaining fixed. This can affect the torque tension relationship