Carriage bolts have a round head that gives a wide load bearing surface with out the need for washers as well as a finished appearance when installed. The square neck on the carriage bolts is designed to fit snug into the mating material so that it prevents the bolt from spinning during the tightening of the nut.
Why Use Carriage Bolts
Carriage Bolts offer a high level of security when securely fastened and access to the nut is not possible, making these screws the go to choice for garage barn doors and all other entry points.
It is advisable to add a washer on the nut side for improved fastening and holding power when joining pieces of wood together. To ensure a snug fit between two metal components, the hole in which the fastener passes through must have an identical size as the square shank.