For example, maybe you needed a three to make a straight.
I like this play if you need the player to your left to lose a high card early, if you want to start the single card count high, or if you did not see a particular low card in the pass. Besides naming the card you passed, you can try naming something else you think will break up his or her hand. This traditional play keeps the player to your left from benefiting from your pass card, no matter what you pass them (assuming you do not pass them any animals: Dog, Dragon, or Phoenix). This allows you to always fish your wish when naming a card for the Mah Jong. Pay attention to what you pass the player on your left.