Peavey bass guitars Owner's Manual page 19

Intonation
A properly intoned bass guitar will sound in tune no matter where you play along
the fretboard. Bass intonation describes the accuracy in relative pitch (of your bass
with itself ) as you play the same note or chord. Intonation is determined by the
length of each string as controlled by the location of each string's saddle. To check
intonation, complete all adjustments to the truss rod and string action, and
tune your guitar. Then, compare the fretted sound of the 12th fret to the
open harmonic of the 12th fret. (Harmonics are created by lightly placing a
finger against a string [in this case, at the 12th fret] and striking normally
with your picking hand. You've done it correctly if you hear a clear, loud,
bell-like tone.) If the notes are the same, no adjustment is required. If they
do not match, you will need to fine-tune each offending string using the
adjustment screws to move the saddle location. If the fretted 12th note is
flat, adjust the saddle toward the neck. If sharp, move it away from the neck.
(Note that on some bass guitars, you will need to loosen strings first before
making saddle adjustments.) Repeat the process until the fretted sound of
the 12th fret matches the open harmonic of the 12th fret.
19