Definition & Meaning of "lag screw"

What is a "lag screw"?

A lag screw is a large, heavy-duty screw designed for fastening heavy materials like wood or metal. It has a thick, coarse thread that provides a strong grip and can hold large loads securely. Lag screws are often used in construction, such as when attaching large beams or posts to wooden or metal structures. They typically require a wrench or socket to tighten and are often used with a washer to distribute the pressure more evenly. Lag screws are ideal for tasks where a strong and durable fastening is needed.