The degree of curvature of the fretplane is referred to as the fretplane relief.
Similarly, the degree of curvature of the fingerboard is referred to as the fingerboard relief.
Here at Plek, we differentiate between the measured relief of the instrument’s fingerboard and fretplane, and the recommended optimal relief for the instrument’s fingerboard and fretplane.
Recommended optimal relief is based on instrument specifications such as action, string gauge, player attack.
Fingerboard and fretplane relief can be altered by changing the adjustment of the trussrod (if the instrument has one).