The front and back surfaces of the fingerboard are not parallel, but have a very slight angle between them (a compound angle, between two corners). The angle provides clearance for the vibrating strings so that they won't buzz against the frets. We have a compound angle because different strings vibrate at different amplitudes. After a week of sanding, and inhaling too much ebony dust, the dimensions we need are achieved.
The next step is slotting the fingerboard for the frets. There is a mathematical formulation to compute the location of each fret, which splits the scale length into the standard Western-style scale. I invested in a good ruler which goes down to 100ths of an inch. We need this accuracy because the location of the frets will determine the intonation of the instrument. If a fret is out of place, then some notes will be relatively out of tune. Even with all the frets in precise location the tonality is not perfect. Back in Bach's time the well-tempered tuning was conceived which achieves a balanced tuning across all the different keys. This means some notes will be a little out of tune in some keys, but overall its pretty good. Instruments such as the violin don't have to worry so much about this since the tonality is determined by the player's finger position and can be adjusted for each key.
Now we remove material from the fingerboard that would hang over the soundhole.
The fingerboard is ready for the gluing. We use brads in the 1st and 11th fret locations to secure the fingerboard from sliding while it is glued and clamped. The brads are removed after the glue sets. We used a similar technique to glue the neck to the soundboard, and you can observe two small dots on the soundboard close to the junction with the neck. Those brads were also removed.
We use lots of pressure to glue the fingerboard to the neck and sounboard. I also used too much glue, but it is better than not using enough.
The excess material on the neck that extends beyond the the fingerboard is shaved off with a spoke-shave. This tool is a lot of fun to use.
The fingerboard is ready to receive the frets now. The frets are cut from a coil of fret-wire and then tapped into each slot. The neck needs to be well supported so that the impact of hammering the fret won't be absorbed by the body.
The last few frets are pressed into their slots so that there won't be too much banging over the soundboard.
A lot of work has been done between the two pictures here. After all the frets were installed, the plane of the frets was trued with a mill file. Then a special file that has a concave contour is used to re-crown the top of each fret. Finally, each fret is carefully poslished using sandpaper and steel wool, taking special care not to mar the surface of the fingerboard.
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