Feeler gauge

A set of thin steel leaves of stated thickness, used to measure a gap by sliding the smallest leaf that will still fit.

For setup purposes it is the tool for reading neck relief: the leaves are stacked until they just fill the space between the eighth fret and the string while the first fret is held down, and the total gives the relief figure directly. The same technique reads a nut slot, a pickup-to-string gap or a bridge clearance. Because the leaves are numbered, the measurement can be repeated, which is what turns a vague feel into a setting anyone else can duplicate.

Example: holding the low E at the first fret and fitting a 0.010 inch leaf under it at the eighth tells you the neck's relief is ten thousandths.

Feeler gauge

See also