These steel screws have corrosion-resistant finishes. Also known as lag bolts, they have a hex head for a secure grip with a wrench. They press threads into material for a tight, secure hold. To prevent splitting, drill a pilot hole slightly smaller than the screw. Length is measured from under the head.Hot-dipped galvanized steel screws have a thick coating for better corrosion resistance than zinc-plated steel screws. They're a good choice for ACQ-treated (arsenic-free) lumber.