Checking, then raising the opponent's bet.
Written x/r. When facing a c-bet in the BB, use it with two pair or better and strong draws (12+ outs). The opponent's c-bets include many weak hands, so build the pot with strong hands and push them off with strong draws. In Limit Hold'em, check-calling the flop and check-raising the turn gets two big bets in. On the river the opponent often just checks behind, so a river check-raise usually doesn't pay.