I work with jigs a lot in cutting the jigsaw puzzles. I’ve been aligning the material to a piece of electrical tape on the left rail of the crumbtray, and that has worked pretty dang well for me. Why not have something a little nicer, especially if you can do it for basically free, right?
These rulers attach to the left rail and the right rail of the crumbtray using veneer (I used PG maple veneer). The original AI file is included (with modifiable text) along with the SVG that has text outlines.
The curve could use a tiny bit of smoothing but it’s close enough you can’t tell that it isn’t perfect.