Okay, so about 13.5 years ago I took a job in the greater New Orleans area. Some of the women who worked for me had been working in the cafeteria for years. She was well into her 70's and though slowing down and sometimes resisted change was always extremely helpful. One day I was struggling to get open a jar. I had tried everything I could think of. She comes up and this is how she did it:
Bang on the lid with a knife or tap the edges of the lid on the counter.
Then, with the heal of your hand, hitting upwards, hit bottom of the jar.
The action of hitting the bottom of the jar forces the pressure up and releases the seal on the lid.
For me this works every time, now, sometimes I have to repeat it because I either didn't tap the lid enough or I didn't hit the bottom well but, it works. My husband now comes to me to get his salsa and pickle jars opened.