Final answer:
The most common bolt for outdoor deck projects is the carriage bolt, known for its smooth, round head and self-locking square underside, making it aesthetic, safe, and secure for such applications.
Step-by-step explanation:
The most common bolt sold for outdoor deck projects is the carriage bolt. Carriage bolts are favored due to their smooth, domed heads that do not have external drive slots. The round head of a carriage bolt provides a finished look that is aesthetically pleasing and also safe, as there are no sharp edges to catch clothing or skin.
Furthermore, the underneath part of the head is squared to lock into place, which prevents the bolt from turning as the nut is tightened. This self-locking feature is advantageous during assembly, especially in hard-to-reach places.
Installation of carriage bolts typically involves drilling a hole into the wood, which is slightly larger than the bolt itself. Once inserted, tightening the nut on the other side pulls the square underside of the bolt head into the wood, locking it in place. Because of their durability and security, carriage bolts are common choices not just for deck projects but for other outdoor wood constructions like playground equipment, fences, and outdoor furniture.
Other options for deck projects include lag bolts and hex head bolts, but these are not as common as carriage bolts. Lag bolts, also known as lag screws, have aggressive threads and are used for heavy-duty applications. Hex head bolts may be used when a flat surface is not required, and the side of the bolt will not be visible or be subject to wear and tear.