What do ladder bars do ?

Ladder bars, I have always seen them on coil spring rears a la Chevelles and what not... a crusty old Mopar guy told me years ago that a Mopar rear with properly adjusted pinion snubber didnt need Lakewood "slapper bars" as he was chewing me out for running them on my Dart. I would assume the same with ladders. Now if it is a raced out/ tubbed tubualr race frame with a coil rear then yes...