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 galvanized steel for great corrosion resistanceSelf-locking square neck and coarse threads fasten very securely6 in. thread lengthIncludes 25-pieces to complete your projectBuy by the box and saveHead code CRA. Cancer and Reproductive Harm – https://www.p65warnings.ca.gov/