Is it a Lag Bolt or a Lag Screw?

One of the most common questions we get here is that question. Even from our own staff! Most of the calls we get ask for a lag bolt, most people call it a bolt but in fact it is a screw. A very quick tutorial on the difference between a bolt and a screw (there are much more in depth explanations but for simplicity): Screws are used in situations where the component has an internal thread or where the thread will be cut into, whereas bolts are for attaching un-threaded components with the use of a nut. This can get confusing with certain screws like machine screws that can be used with or without nuts but for the most part it can be pretty clear to know if you are using a bolt or screw by what the part is going into. Going into wood, plastic or metal and making its own thread, or the component is pre-threaded - it's a screw! Two pieces of material with a hole in it and use a nut on one side, it's a bolt!

So by that definition alone it is a screw! Lag screws are used for wood, cut their own thread and no nut required.

Lag screws are heavy duty screws usually used to fasten heavy lumber together or connect lumber to masonry. For example commonly used in deck and dock building.