I have used this for quite some time, but as I was using it today I thought about the forum and thought I would share this jig I use.

It will help you when you are mounting your neck so that you can be assured that it is in line and centered on the guitar... even a tiny bit off of center will show up dramatically. It also will place your bridge in the perfect location every time with no measuring. It ends all of that fussing with straight edges and rulers and wondering if your bridge is located in the perfect spot.

This jig slips over your fretboard and has ears on each side to hold it in the perfect centered position. The top portion of the jig was made by cutting the plexiglass to the same dimensions as my normal fingerboard size and then 4 "ears" were super glued on to hold it in the exact position. Notice that there is a scribed line down the center on the lower portion. This will tell you whether or not your neck is centered while you are sanding it into position.

At the lower end of the jig, there is a saddle glued to it. I made this jig by using a Martin D35 guitar that I knew was in perfect condition for the scale and intonation. By butting the neck end of the jig up against the nut and sliding the glued on saddle into a saddle slot on your new bridge, it will locate the bridge for you and you can be assured that it is in the perfect spot for a 25.34 Martin Scale. no measuring needed and guaranteed to be centered also

This was all made out of scrap lexan I had laying around the shop. That is why you see the "extra" piece of lexan scarfed onto the end of the jig in the last picture. When Imade this jig, I hand sanded the saddle end of the jig until it just would drop into position while the nut end was firmly pressed against the nut of the known good guitar.  WHen it just would drop into position, I super glued it in place using an excellerator to keep it from gluing itself to the saddle of that guitar. This is how I am so sure that this works and is perfect intonation.

Of course if you use this jig, you would need to make a different jig for every nut width you use and also for each scale. All of the guitars I have made so far all use 25.34 scale, so the one jig does it all for me. My next model will have some self-centering adjustable ears on it so that different fingerboard widths can be used with the same jig. I may get really inventive and also have an adjustable scale length as well. for now, this is all I need.

Hope this helps!