Decline to win a trick, often with the intention of disrupting opponents’ communications. This is a common technique and is available to declarer and the defenders.
South plays in 3NT and West leads the ♠J. Declarer calls for the queen, which East wins with the ace. Back comes a spade.
If declarer wins the second spade, East will have a third spade to lead upon getting in with the ♦A. So declarer’s correct play is to hold up the ♠K until the third round.
Declarer plays on diamonds and it is East’s turn to hold up. Winning the first or second diamond would allow the diamond suit to produce four tricks. Instead, East holds up the ♦A twice, taking it on the third round.