I suppose you knock three times and ask for St. Peter

[Billy, Max and Jimmy are going over blueprints of the prison] Jimmy:
There's two ways out, I figure. Over the roof, but that's only one person, maybe two. The other way is under. Billy Hayes:
Tunnel? Jimmy:
It's already built! There's a basement substructure where they used to keep weapons and stuff, but beneath that there's these old catacombs that the Christians built about a thousand fucking years ago to bury their dead. We're sitting right on top of it - here. The Kraut said there's a whole bunch of hollow sealed shafts sort of like dumbwaiters running along this wall. One of them is right in there, right next to our shower. We can get in there, he says, we can get down into the catacombs. With the three of us working... Max:
[tapping at the wall]
Gotta be here someplace. Thought I heard a couple of dead Christians singing down there. Jimmy:
Stop shitting me, man! Billy Hayes:
But how would you get into the shaft, Jimmy? Max:
I suppose you knock three times and ask for St. Peter