Lag Screw, 5/16 in, 4-1/2 in, Steel, Zinc Plated Hex Hex Drive, 50 PK, Midwest Fastener, Mfr#: 01307

A lag screw is similar to a wood screw, but generally is much larger with a hexagonal head. Lag bolts are designed for securely fastening heavy timbers to one another, or to fasten wood to masonry or concrete.