A guitar’s neck should be straight to ensure proper intonation and playability. Checking the straightness of the neck is a relatively simple process that can be done at home with a few basic tools.
The most common way to check the straightness of a guitar neck is to use a straightedge. A straightedge is a long, straight piece of metal or wood that can be placed along the length of the neck. If the neck is straight, the straightedge will make contact with the neck along its entire length. If the neck is bowed, the straightedge will only make contact with the neck at the ends.