Notched straightedge
A straight metal bar with slots cut to clear the frets, so it rests on the fingerboard itself rather than on the fret tops.
That distinction is the entire point. A plain straightedge laid on the frets tells you about the fret plane, while the notched version tells you about the fingerboard's own straightness underneath it. When the two disagree, the frets are not uniformly seated, and that is precisely what a levelling job corrects. It is also used to judge relief directly against the board rather than against the fret tops.
Example: a notched straightedge showing a bow while the fret tops look flat means the frets vary in height and need levelling.
See also
Related
- PageRelief
- PageTruss rod adjustment
- PageAction gauge
- PageAged finish
- PageBack bow
- PageAaron Dessner
- PageAce Frehley
- PageAd-Rock