Torque Washers  This washer was specifically designed to go under the head of a carriage bolt. The outside diameter is 1.10", the square center hole is just over 1/4". The three prongs on the washer dig into the wood around the bolt, and prevent the carriage bolt from turning. By using this washer, the pressure from the head of the carriage bolt is spread over a much larger area, and prevents damage to the wood framing of exhibit panels.