The explanation that I read is that churches are built as cheaply as possible, so the lock on the door is of such poor quality that you could open it with a beer can opener. That explanation probably dates back to when doors had actual keyholes.
When I was in high school my friends and I all thought calling a beer can opener a "church key" was a derogatory reference to the Christian churches that disapproved of alcohol consumption and also a sarcastic comment on "Christians"' who sinned all week and went to church on Sunday.
I still have no clue what Jar's single right answer is.....
42 should cover it.
What if Eleanor Roosevelt had wings? -- Monty Python
One important characteristic of a theory is that is has survived repeated attempts to falsify it. Contrary to your understanding, all available evidence confirms it. --Subbie
If evolution is shown to be false, it will be at the hands of things that are true, not made up. --percy
The reason that we have the scientific method is because common sense isn't reliable. -- Taq