Washers are usually used to help distribute the load of a threaded fastener like a bolt or nut. Washers also can act as spacers or be used to help fastener from coming loose with the help of a lock washer, or be used as vibration absorption or sealing properties as with a bonded EPDM sealing washer that are common with TEK roofing screws. Whatever need you have, we sell the washers for it.