Neil wrote:

Hi Josh,
can you let me know if my understanding on how to use this is correct, for the roller and idler parts:
- roller - surface to left of roller "bump" on gauge rests on outer flange when double flange, surface to right of roller bump rests on inner flange on both rollers
- idler - surface to left of idler "bump" rests on idler center rim. Flip to measure other side of idler

Is that correct?

Best way to figure how it works, is to print one out and try it out on the tractor, it starts to make sense that way.