Carriage Bolts

A carriage bolt, also known as a coach bolt, has a domed or countersunk head and the shank is topped by a short square section under the head of the bolt. The square section grips into the part being fixed, preventing the bolt from turning when the nut is tightened. Carriage bolts are often used to fasten wood panels or board to masonry or to one another. The square shank of a carriage bolt allows it to lock into place when inserted into a round hole in wood or a square hole in a metal strap, the unthreaded square shank pulls into the wood creating a tight connection.