Prior to gluing the fretboard, you should fit the neck to the guitar. If it is a removable neck, make sure it fits and is setup properly. If it is a fixed neck, make sure all of the joints are glued properly, tightly and the neck angles are correct.
Tools and Materials:
Digital Vernier Calipers
Woodworkers Marking Knife
Plastic Tipped Hammer:
36″ Steel Straightedge
Test Fit The Fretboard:
The fretboard should be all ready to go. The fret slots cut, the taper cut and the fretboard cut to exact length. Also if it is a bound fretboard, that should be complete as well.
Strike a line down the exact center of the fretboard with a sharp Woodworkers Marking Knife.
Set the fretboard into position and adjust the lateral angle by testing it against the global centerline of the guitar. Test measure the fretboard at the nut end and at the sound hole end. This measurement should be made with the Digital Vernier Calipers.
I usually strike a line on the guitar top to locate the saddle with a very sharp pencil. Then I strike a small mark from the extended edge of each side of the fretboard on this line by using a 36″ Steel Straightedge. Then I compare the two marks and make adjustments as necessary.
Next, take a fine dry mark, like a ultra-fine Sharpie and mark the fretboard position edges clearly on the face of the neck.
Clamp The Fretboard In Place:
With the fretboard correctly placed, clamp lightly into position with a couple of Wooden Cam Clamps. Take care not to disturb the fretboard positioning.
Next, place a 1/32″ drill bit in a hand drill and drill two holes through the fretboard and into the neck.
Here are the two hole locations you should use:
The first location should be through the first fret channel, about 1/2″ away from the treble edge of the fretboard.
The second fret location should be through the 12th fret channel, about 1/2″ from the bass side of the fret board.
The holes should not be drilled any deeper than about 1/4″ into the neck. The best way to guard against this is to measure the correct depth on the drill bit and turn a strip of masking tape around the bit to act as a depth gage.
Drive Registration Pins Into The Neck:
Now we should drive the fretboard registration pins into the guitar neck. I usually use very small brads – about 3/4″ long. Tap them into place in the holes you drilled. Do not drive them too much deeper than the hole depth to run the risk of exposing them during final neck shaping. When driving in the brads, keep them perfectly vertical.
Next take a End Nippers: (don’t use your fret nippers) and cut the brad off about 1/16″ or so above the surface of the fretboard. If you need to drive it a bit more into the neck do so now. File off the top of the brad with a fine file.
GLS Tip: These registration pins should be tight fitting without any play. This means that they need to be slightly larger in diameter than the hole you drill for them.
Test Fit The Fretboard
Now fit the fretboard over the registration pins. You may need to enlarge the holes just a bit in the fretboard so the fretboard slides over the pins easily, but not loosely. Check the fit by trying to move the fretboard with your hands. If it is secure, you are ready to glue in in position.