Here's an online company selling some useful guitar setup tools.

[Joe Garfield]

Thanks for the link, Doc. I was looking at notched straight-edges, a little cheaper than StewMac. They have edges for Fender, Gibson, and PRS guitars. Do you know what the difference is? What about my PBG kit G-style guitar, looks like an Epiphone? Thanks.

Edit: I saw a pic of the Skyscraper tool and figured it would be way more expensive - their stuff looks VERY nice and reasonable, too! Nice link, Doc!

I got this straight edge which has Gibson (24.75") on one side and Fender (25.5") on the other. Like Doc said, that covers the vast majority of electric guitars other than PRS. The one linked by Doc looks a lot more robust but most people seem to use one similar to this:
https://www.ebay.com/itm/Guitar-Neck...item3abf6bd654