Third Hand Plays High but cheaper of touching cards

“highest card necessary”
 

After ♠3, ♠2, you must play ♠Q, the cheaper card. If West sees the trick proceed ♠3, ♠2, ♠K (erroneously), ♠A, he should deduce that declarer holds ♠Q.

After ♥3, ♥2, you play ♥10. When West sees this force out declarer’s ♥A, West can deduce that you also have ♥QJ – or declarer would have won the trick more cheaply.

West leads ♦3, dummy plays ♦2 and you as East should play ♦9, the cheaper of your highest cards. When West sees this force out declarer’s ♦K, he can deduce that you also have ♦J10 – or declarer would have won the trick more cheaply.

It’s the beauty of the partnership. It doesn’t matter to you which of the equals you play. But it helps partner hugely to draw the right inferences.