A lag screw is also known as a lag bolt, and it is one of the best choices for hardware when it comes to DIY woodworking projects. Lag screws have a sharp point at the end and a screw head that can be either square or hexagonal. Most lag screws are manufactured out of galvanized steel, and available in wide range of sizes.
Step 1 -- Line up Wood Pieces and Drill Pilot Hole
Align the wood sections of your construction project and hold them together with wood clamps. Drill a hole with the smaller drill bit where you will be installing the lag screw.
Step 2 -- Install Lag Screw
Use your hex-head screwdriver to start screwing the lag screw into the pilot hole. Secure the locknut with the screw in order to distribute the pressure evenly and keep the lag screw from becoming loose over time.
Step 3 -- Finish with Screw Bit
Attach the correctly-sized screw bit to your drill, and finish installing the lag screw and locknut. Remove the wood clamps once the lag screw is all the way in.