It's applicable to any guitar, though it's far less likely to be an issue on a bolt-on neck guitar.

I've done the same thing again now the neck's glued on. You really need to clamp the neck in place when testing, as it's amazing what a bit of extra force can do to the final neck angle.



The straight edge is now touching the top of the bridge, with the straight edge being raised off the end of the neck slightly (less than 1mm). If the straight edge was touching the top of the saddles when flat on the neck, then that's really about as low as you'd want the straight edge to be pointing. The bridge will have to be raised up by 2mm-2.5mm from that point in order for the strings not to hit the frets. There's normally 1mm or so of rim on the post insert, which will account for some of that height adjustment, so you've then got maybe 1mm of height adjustment to do on the post screw.

If there's a gap between the straight edge and the top of the saddle (as in the first photo I took if it), then the bridge will have to be raised up on the posts by the gap height+ approx 2mm extra for a low action guitar.

You don't want the bridge to sit too high, as you then have very few post screw threads in the insert, and the play in the screw threads allows the bridge to rock back and forth more. So maybe 5-6mm maximum. Too high, and the neck angle needs to be reduced.

Conversely, if the end of the straight edge would hit below the slot in the saddles, then you'll find that the strings will sit too high off the fretboard and you've got no way of lowering them as the bridge is as low as it will go.

I had this on my first ES-1, tried filing the bridge so it sat lower (to no avail) and then finally managed to find a really low profile bridge (a Goldo Lowrider) which allowed me to get a really nice action on the guitar. But they are rare beasts, seem to exist in shops in France and Germany only and may now even be discontinued, as everywhere I looked at that sold them were out of stock (and they only do them in nickel, no gold option).

So view the straight edge as the string, hold it off the end of the fretboard by say 2mm, and where it passes over the bridge position, that's pretty much the height the bridge will need to be set to. If it can be set to that height without being too high off the body, then all is well. But too high, or an inability to set the bridge low enough, and you need to do something about the neck angle before the neck is glued in and the angle is fixed.

On a bolt-on, you can use shims at one end of the neck pocket to increase or decrease the neck angle if necessary. But generally on a bolt-on, the neck is parallel with the body (which is generally flat) so the string height at the bridge is determined by the neck height/depth of pocket and so by how much the neck sits above the body. It's a lot easier to get the bolt-on pocket bottom parallel to the top than it is to make a correctly angled pocket for a set neck guitar.