What does the bolt inside neck of your guitar do?

The bolt inside the neck of your guitar is called the truss rod. It is used to adjust the relief, or curvature, of the neck. By turning the truss rod clockwise, you can increase the relief, which will make the strings higher off the fretboard. By turning the truss rod counterclockwise, you can decrease the relief, which will make the strings lower off the fretboard.

The proper amount of relief is a matter of personal preference, but most guitarists prefer a slight amount of relief, as it makes the guitar easier to play. Too much relief can make the strings buzz, while too little relief can make the strings feel stiff and difficult to bend.

If you are not sure how to adjust the truss rod on your guitar, it is best to take it to a qualified guitar technician.