Back bow

A neck whose middle curves away from the strings instead of being slightly concave, so relief measures as a negative number.

When a neck back-bows, the middle of the fingerboard rises towards the strings, and the result is rattling and buzz from around the fifth fret upward with no way to fix it by raising the action at the bridge, because the problem is above the bridge. Truss rod adjustment is the first response: loosening it lets string tension pull the neck forward again. If the neck will not move, the rod may be exhausted, and heat treatment or fretwork is needed instead.

Example: a guitar that buzzes only in the middle of the neck and plays cleanly high and low is usually back-bowed rather than badly set up.

Back bow

See also