Product Description The Hillman Group 812048 Hot Dipped Galavanized Hex Lag Screw, 5/16 X 4-Inch, 50-Pack From the Manufacturer Hex Lag Screws are used for directly fastening into wood surfaces. They are used with a lag shield, and lag screws can be used in masonry applications. The hex head is six-sided and ideal for easy driving and quick installation. The threads on lag screws are designed to embed into the wood, rather than relying on a nut to secure the connection.