To do
something hammer-and-
tongs is to
work very
hard at
something, and to
do it for
quite a
long time.
Example :
"God. My damn roommate and his girlfriend were going at it hammer-and-tongs again, and I haven't been able to get in my room for over an hour!" It's meant to evoke the image of blacksmiths shaping metal, constantly pounding on it, never stopping until it is finished.