What I really came to this thread for is the following question.
I had canned some mushrooms in the summer. Now one of the jars I just can't open for the life of me, no matter what I do. It is not about my hands slipping, so no towel/sandpaper and whatever else will help. The lid looks like this:
So it is not the suction/vacuum that keeps it from being twisted.
Any ideas on how to open it?