We often use stepped "reach gauges" for machine guards used in manufacturing and such: https://www.mcmaster.com/gauges/machine-guard-safety-gauges/ https://www.

We often use stepped "reach gauges" for machine guards used in manufacturing and such: https://www.mcmaster.com/gauges/machine-guard-safety-gauges/ https://www.mcmaster.com/gauges/machine-guard-safety-gauges/ Not too expensive though.