Description
5/16"-18 x 4-1/2" Zinc Grade 2 / A307 Carriage Bolts (50 pcs.) Diameter: 5/16" Length: 4-1/2" Material: Steel Finish: Zinc Head Style: Carriage Thread Size: 18 (Coarse) Thread Length: Full Hardness: Grade 2 / A307 Type: Carriage Bolt Square-Depth: 13/32" Box of 50. A carriage bolt has a domed or countersunk head, and the shank is topped by a short square section under the head. The square section grips into the part being fixed (typically wood), preventing the bolt from turning when the nut is tightened.