Declarer can sometines keep a dangerous defender out of the lead by giving up a trick in one suit in exchange for a trick in another.
Dealer West All Vul
 K 8 5 8 5 2 A 4 K J 7 3 2 |
||
| 9 A Q 10 9 4 K Q J 8 5 8 4 |
10 7 3 J 3 10 7 6 3 2 Q 10 5 |
|
| A Q J 6 4 2 K 7 6 9 A 9 6 |
The Auction:
| West | North | East | South |
| 1 |
Pass | Pass | 1 |
| 2 |
3 |
Pass | 4 |
| Pass | Pass | Pass |
Lead: K
West leads K and it is not difficult to see that South is threatened with the loss of a club and three heart tricks. He would like to be able to establish club winners without letting East in to play a heart through the King.
This is neatly accomplished by playing a low diamond for dummy on the first trick. Say that two high tumps from hand, then Ace and King of clubs and a club ruff, he returns to dummy with K and discards two hearts on the established clubs, making an overtirck.