The Assessment Comes First
A straight edge laid along the fret tops reads the neck's geometry in seconds: relief (the intentional forward bow under string tension), back-bow, or a hump at the body joint. A feeler gauge quantifies the gap at the seventh fret when the first and last frets are fretted, giving the technician a relief figure to compare against the maker's specification or the player's stated preference. These two readings — straightedge and feeler gauge — determine whether the job is a truss rod adjustment, a full level-and-crown, or both.
The truss rod adjustment and the fret-level pass are scheduled as distinct operations. A rod tweak needs time to settle — often twenty-four hours — before a level pass makes sense. Running both jobs in the same session without that interval produces a fret job that moves as the neck continues to respond, which is a poor outcome for the shop and the instrument alike.
When a level pass is warranted, a long, flat reference beam or a precision straightedge confirms which frets are proud before any abrasive work begins. The level removes material from the tallest frets until the plane is consistent; the crowning file then restores the correct radius to each fret top, because a flat-levelled fret buzzes and chokes bends. Final polishing brings the surface back to the finish expected on playable frets. The whole operation is read through the geometry of the neck at every stage, not executed in a fixed sequence of steps.
What makes the work skill-dependent rather than procedural is the diagnostic layer. The same symptoms — buzz on the fifth fret, dead note at the twelfth — can originate from relief, fret wear, a high nut slot, or a combination. According to Fender's own setup documentation, relief targets vary by string gauge and playing style, which means the technician's first question is always about how the instrument is actually played.