Carriage bolts have a dome shaped head with a square shoulder underneath. This square shoulder prevents the bolt from turning during assembly. Carriage bolts provide a smooth, finished look that is aesthetically pleasing. The bolts are useful when working with wood as the bolt is held in place while other wood members are joined together, eliminating the need to hold the bolt while it is being tightened.
Mark the location for the carriage bolt using a pencil or marker.
Choose a drill bit that is the same diameter as the threaded portion of the carriage bolt. Drill the hole for the bolt through the wood. Drill perpendicular to the surface of the wood.
Insert the carriage bolt into the hole. Place a scrap block of wood on the head of the bolt and hit the wood. This will set the bolt in the wood, keeping it from turning freely during assembly.
Place a washer and nut on the opposite end of the bolt. Tighten the nut with the appropriate sized wrench. The shoulder of the carriage bolt will draw deeper into the wood. The carriage bolt should sit flush with the surface of the wood when fully seated.
Use finishing nails as shims if the bolt does not seat properly.