I don't have much experience in creating environments, and my understanding of them allows me to create environments which do something at the beginning and at the end (like for instance, in a "proof" environment, I can begin it with "Proof." and end it with a little square in the bottom right.
What I want to do now is slighty more complicated (so it seems to me), I just want something looking like
Proof. | | | content here | | | end of proof
I want those vertical dashes to be a straight line from bottom to top. Any way I could be able to do that?