the neck needs to be adjusted as straight as possible and strung to pitch.
The guitar is put into the neck jig and the neck adjusted straight again with the strings removed.
After measuring the frets they are leveled using a long sanding block being careful to maintain the fingerboard radius.
The frets are then rounded or “recrowned” using a 3 corner file with a safety edge and special crowning files.
The fingerboard is taped off and the frets are sanded and polished.