Electric Guitar Low Electric Guitar High Acoustic Guitar Classical Guitar Bass Guitar, etc. This is a scale for checking and adjusting string height. How to use: For guitars, adjust by placing the scale at the 12th fret on the 1st and 6th strings. For bass guitars, it can be used for up to 6-string basses. Why not check your own guitar or bass? The back side is a scale that shows the groove spacing according to the neck width of guitars and basses. This is a convenient scale to have.