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.

Diameter: 5/16"
Length: 3-1/2"
Material: Steel
Finish: Hot Dip Galvanized
Head Style: Carriage
Thread Size: 18 (Coarse)
Thread Length: Full
Hardness: Grade 2 / A307
Type: Carriage Bolt
Square-Depth: 3/16"

Diameter: 5/16"
Length: 6"
Material: Steel
Finish: Hot Dip Galvanized
Head Style: Carriage
Thread Size: 18 (Coarse)
Thread Length: Full
Hardness: Grade 2 / A307
Type: Carriage Bolt
Square-Depth: 3/16"