A built-in flange protects surfaces from splitting and pull-through by spreading pressure over a large area. These screws won't rust, so you can use their coarse threads to secure posts and beams outdoors. They also won't degrade from chemically treated wood, such as ACQ-treated (arsenic-free) lumber. The hex head's six contact points keep sockets in place to avoid slipping and stripping the drive. To tighten, use a wrench or six-point hex socket. Also known as lag bolts.

Drill a pilot hole slightly smaller than the screw to prevent splitting. Head height includes the flange. Length is measured from under the flange.