Carriage bolts have a smooth rounded head with a square neck underneath that locks into wood when tightened. Use with a pre-drilled hole and secure with a hex nut and washer to prevent spinning. They are great fasteners for decks, play equipment, docks, fencing, and furniture.Unique design is great for connections where the head is not accessible for tighteningMade from zinc plated steel for durabilitySelf-locking square neck and coarse threads fasten very securelyFully threadedIncludes 100-pieces to complete your projectHead code AEA. Cancer and Reproductive Harm – https://www.p65warnings.ca.gov/