The grade 5 steel carriage bolt with zinc plated finish has a square neck and round head and meets American Society of Mechanical Engineers ASME B18.5 and Society of Automotive Engineers J429 specifications. Grade 5 steel, composed of quenched and tempered medium carbon steel, is often used in applications where strength is the primary concern. The zinc plating offers corrosion resistance and has a reflective appearance. The square neck prevents the bolt from turning once installed, even when a nut is tightened. The round head has a domed shape.
Carriage bolts, also called round head square neck bolts, are square-necked threaded fasteners commonly used in wood fastening applications. The bolt's square neck prevents it from turning once installed using a nut.