When I was a about 12 (I guess) the Cosby Show was pretty popular and I remember this scene where they were trying to open a jar. One of the kids hit the bottom of of the jar with their palm a couple times and the lid came right off with little effort. I always thought that seemed like a great idea, but I could never get it to work. I just end up with a sore palm.
I have also used one of those "rubber husbands" (or jar grippers) before and for easy jars those do work. You put it on top of the jar and just open as usual. It creates a "grippy" surface and helps you hang on better.
My favorite way to almost always successfully open a jar is the hit the metal lid with the back of a wooden spoon or butter knife about 4 times (at 12:00, 3:00, 6:00 and 9:00, as on a clock). This breaks the seal and that top should come right off.
Lastly, if all else fails, run the jar under hot water in the sink for a few minutes, dry it off and try the knife trick.
And if those don't work..eh.. you didn't want what is in that jar anyway. Right?
Do you have a full proof trick to open a jar or a funny story about it? Leave a comment below.