A guy drags a chain into a bar

A guy drags a chain into a bar. The bartender asks
"why are you dragging that chain behind you?"
The man replies
"Man, you ever try pushing one of these?"

This is a bar joke. The humor is centered around a misunderstanding. The bartender - when he was asking why the guy was dragging the chain - really cared more about why he was transporting the chain around, however the man thought that the bartender was asking why he was dragging it as opposed to transporting it around in another manner.