Measuring a sealed unit thickness

[mklotz]

Despite seldom having to make obstructed measurements like this, I like this idea of resettable calipers. I can think of a few other uses for this added feature. If one has calipers with a screw adjustment, adding a stop nut to the threaded rod provides this refinement.

Other approaches to the problem...

Measure across a block held to one side of the glass. The block must be large enough to force the calipers to be opened far enough to clear the obstruction. Subtract block width from caliper measurement.

Simply open the calipers far enough to clear the obstruction and measure their opening. With one arm against the glass, measure the distance of the other arm from the (other side of) the glass. Subtract the latter measurement from the former.