what is an an flat washer
Flat washers may be used on either the bolt side, the nut side or both sides of the fastener. Flat washers help to distribute the force of tightening the nut by increasing the surface area. They may also be useful as spacers when a bolt may be a bit too long for the job. Lock washers are typically used on the nut side of the fastener. The most common type of lock washer is the split coil washer.