I worked at a plant years ago where the managers would caulk welds on the tractor trailer frame that where missed during production, then paint over it once it tacked up, it appeared to be a weld and without touching it, I never would have known. I missed a DOT tag and was installing it out in the yard during lunch when I saw 3 white hats mingling around a finished frame. I hid out until they left, then wondered over to see what they were doing. Fortunately it was a bright day and I saw the difference in the wet paint band against the already dry painted frame. When I dabbed my index finger to see if the paint was wet, the caulked weld came with it.
It change my life and once I saw that, I became a quality inspector and paid to go to school on my own dime. That was 1986.