These extremely sturdy fasteners are usually used to connect heavy lumber or other heavy materials that are bearing an intense load. These screws differ from normal wood, self-drilling or sheet metal screws. Compared to most ordinary screws, lag screws are massive in size. Most lag screws are at least one inch long and 1/4-inch thick. For example, wood screws are used when connecting an application with only wood materials. These wood screws boast coarse threading, but that threading does not encompass the length of the screw. Normal wood screws thread as they enter the wood, where lag screws require a hole to be drilled first. Lag screws also use a nut to add extra strength and security to help hold things together. Used for intense load applications, lag screws can support a much heavier load than the average sheet metal or wood screw.