Ah, I wasn't clear...
Originally Posted by semi-ambivalent
I don't even turn the enlarger on when I'm checking with the glass. It just clamps in place of the negative carrier so that I'll have a dead-level surface that projects out far enough for me to get a measurement between it, the baseboard, and the lens stage. I use a large machinist's square to check for a basic level, and I usually throw a digital level on top of the glass as well. That will get me well within tolerance.
My grain focuser check is simple: I have a folder of film-speed test negatives, and I just pick one with noticeable grain (Tri-X in Diafine is good) and throw it in a carrier after I have my basic level. I open the lens midway - open enough to see, basically - and then focus at the center of the projected "image." Then I check out at the extreme edges...theoretically, everything should be pretty sharp. It's worked so far...so either I'm doing it wrong, or exactly right.