What is a lag bolt?

• A. A small wood screw
• B. A drywall screw
• C. A lag bolt is a type of nut
• D. A large wood screw with a square or hex head that can be turned with a wrench

Answer: (D)

A lag bolt is a heavy-duty wood fastener designed to pull wood together or anchor into thick wood. It has a large diameter, deep wood threads, and a square or hex head that you turn with a wrench or socket, not a screwdriver. This combination—size, wood-threading, and a wrench-driven head—distinguishes it from small wood screws or drywall screws and confirms it isn’t a nut. To install, you typically drill a pilot hole and drive the lag bolt with a wrench until it’s snug and secure.