A lag bolt is used in wood construction to assemble structures such as decking, bridges and beams. A lag bolt does not have a nut and is actually a screw. Lag bolts, indeed, are sometimes called lag screws. The advantage of a lag bolt is the amount of force it can create and the sharp point at its end, which make it ideal for connecting wood pieces. The key to loosening a lag bolt is to not crack the wood material around the bolt.
Things You'll Need
Open-end wrench or box wrench
Inspect the lag bolt head to determine the correct tool to use to remove it. Some may take a open-end wrench or a box wrench, a ratchet or a screwdriver. Using the right tool will make the job easier and will reduce the chance that damage will occur to the material the bolt is fastened through.
Apply the tool to the bolt. Make sure it is snugly affixed to the bolt. If it is not, you run the risk of stripping the bolt.
Turn the bolt counterclockwise slightly to determine the amount of torque you'll need to remove the lag bolt. Slowly increase pressure on the wrench or other tool until the bolt begins to turn, rather than suddenly exert great force on the tool, to get an idea of how much force you'll have to use to turn the bolt out. You do not want to use too much torque, or you may damage the material around the bolt.
Continue to turn the bolt to the left (counterclockwise) until it is out of the material.