NavList:

>>If you simply want to level some surface, find a fairly level flat surface. On this surface will be some line that is level. Place the level on it and rotate the level until the bubble is central. Place a heavy straight edge alongside it to keep the alignment and reverse it end for end. If the bubble remains central then the level is good for use. If it does not, adjust the vial to remove half the difference and repeat the exercise.<<

Bill, in these six sentences I learned more about how to calibrate a machinist's level than I did in the whole booklet that came from the manufacturer.  Thank you so much for this.  I was able to dial in my level last night, sitting on the concrete floor of my basement, and using a marble block, which normally lives out its life as a bookend, as the "heavy straight edge" you refer to.

I expect that the tool-making plant that manufactured this level of mine had the owner's nephew do the English translation of the instructional booklet that shipped with it.  And being the boss' nephew, no other employee, even if he could read & write English, was going to offer corrective comments.

Thank you again for your help!

Bob