The Lag Bolt is the largest screw in the world and shares many characteristics with bolts. They are generally used for heavy load bearing applications and can handle a great deal of shear and lateral load. This is why they are preferred for ledger attachments to rim joists in deck building. They can also be used in concrete or masonry. They are driven into the material using a drill with a socket attachment. Once the screw is in, you use a ratchet to tighten it. Care should be taken when tightening a lag screw as over-tightening can cause the head to snap off inside the material leaving you with a big headache.
When using lag screws it is important to predrill holes with a bit that has a smaller diameter than the size of the lag bolt. This will ensure that the hole is clean when the lag screw is inserted. It is also important to choose the proper length of lag bolt. In general, the lag screw should be at least twice as long as the thickness of the material that it is connecting to. This will ensure that it penetrates and embeds into the second material without bending or breaking.
Whenever possible, it is best to use a lag screw with a threaded tip. This will allow for a quicker and easier installation. In addition, a threaded tip will prevent the lag screw from accidentally turning inside the material when it is being driven into place.