The grade 2 steel carriage bolt with zinc plated finish has a square neck and a round head and meets American Society of Mechanical Engineers ASME B18.5 and ASTM A307 specifications. Grade 2 steel, composed of either low or medium carbon steel, is often used in applications where toughness is the primary consideration. 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.