Pole Line bolts have different types of hardware which are used to fasten them in whatever connection they are used in. It is common for some bolts to be used with a flat or curved square plate washer. The square plates are made from ASTM A36 steel. Flat square plates are used against flat wood surfaces to provide a larger bearing surface as well as to protect the wood from being damaged when tightening the pole line fastener. Curved square plates are used for the same purpose, however have a 4-1/2″ radius curve to fit the contour of the pole.