A dialogue from the movie Body of Lies
Ferris: When they find him, they are gonna torture him and they are gonna kill him.
Ed: You gotta decide which side of the cross you're on. I need nailers, not hangers.
A descriptive context of this dialogue can be found in this review. Is "on which side of the cross" idiomatic? I also can't find any source on "nailers" and "hangers". Does "hangers" refer to "hangmen"? Is this a biblical reference?