98 rear view mirror removal

My rear view mirror rattles and I want to tighten it. however, I can't seem to figure out how to remove it from the windshield. All I see is a small opening on the mount, but I couldn't feel anything with a small flathead screwdriver. My Haynes manual is useless in this regard. It doesn't even list the rear view anywhere in the manual. Any ideas?

Thanks,

Javus

its usually an allen wrench that you can use to tighten and loosen it, if you want it off completely you can take a propane torch to the outside of the windshield where the mirror meets the glass and it heats up the glue, about 2 minutes later it usually falls right off, although you might have to pull it off!

Thanks, I'll give the allen wrench a try. I just want to tighten, no permanet removal.