Often used on posts and beams, the coarse threads on these screws dig in for a firm hold. 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. Length is measured from under the head.

With coarse threads that dig in, these screws secure posts and beams in outdoor and wet environments. They won't degrade from moisture or 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 on 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. Length is measured from under the head.

Fasten decking and fencing outdoors with screws that won't rust. They're often used with chemically treated wood, such as ACQ-treated (arsenic-free) lumber. Also known as deck screws, their trumpet shape spreads pressure to prevent splitting, while the flat head limits snags. The square drive handles more torque than slotted and Phillips drives.

The screw drill tip acts as a built-in pilot, though pilot holes are still recommended near edges to avoid splitting. Length is measured from the top of the head.

Also known as hanger bolts, use these studs to hang, mount, and fasten parts to wood structures. Install them with a stud driver, or create wrench flats by threading two nuts onto the stud and jamming them together.

Lock in for a tighter hold than typical wood screws. Serrations beneath the flat head dig into wood to secure these screws into place. Made of stainless steel, they won't degrade from moisture or chemically treated wood, such as ACQ-treated (arsenic-free) lumber. Also known as a Robertson drive, the square drive handles more torque than slotted and Phillips drives, so it's less likely to slip.

The screw drill tip acts as a built-in pilot, though pilot holes are still recommended near edges to avoid splitting. Length is measured from the top of the head.

Fasten wood to sheet metal while reducing stripping and pull-out. The dual threads on these screws grip both materials at the same time, so they install quickly, require less torque, and resist vibration. Also known as trailer floor screws, these screws are often used to fasten wooden boards to metal trailer frames. With a deep six-lobe opening, Torx drives handle more torque than slotted, Phillips, and hex drives. The flat head deters snags.

Drill a pilot hole slightly smaller than the screw to prevent splitting. Length is measured from the top of the head.