The play of a small card on the second round of a suit in the hope that a particular opponent will have to play the master card.

For example:

To avoid two losers in the suit, you start with a small card towards dummy. After winning with the king, you play small from both hands – there is no point in playing up to the queen since East’s failure to capture the king marks West with the ace.

If you reverse the East-West hands, it would be necessary to play initially from the North hand towards South’s Q-7-6-5; again, you would need to duck the second round.