Now that the fretboard is finished, it can be glued on the
“neck”. For this you need five to six clamps and a
piece of wood slightly smaller than the fretboard to serve as a
clamping caul. A caul is recommended because it distributes the
pressure of the clamps evenly.
Apply a thin, uniform glue film on the back of the fretboard. I do
this with my little finger so my other fingers remain clean. Place
the board on the plank and butt it up against the nut. Then put the
caul on top of it and tighten all the clamps a little. Increase the
pressure on all the clamps in the row until they are all fully
tightened. A clamp should ideally only exert downward pressure when
tightened. There is, unfortunately, almost inevitably some other
force involved which makes the fretboard move on the slippery glue
coat. You can minimize this by clamping small pieces of wood to
both sides and to the end of the fretboard. If you notice that the
fretboard has slipped out of position and can no longer be moved,
remove the clamps and the fretboard immediately, scrape the glue
off carefully and start all over. I had to do this twice on this
guitar until I discovered that it helps if you tighten every other
clamp in the opposite direction, as shown in the picture below.
Wipe off any glue that has been squeezed out with a damp rag.