west	north	east	south
-	Pass	Pass	1♣
1♠	Double	3♠	3NT
All Pass

Team-of-Four (IMP Scoring)
North-South Vulnerable
Opening lead: Six of Spades

After west's overcall, a negative double and east's preemptive raise, south tried three notrump, and west led the spade six.
 
A winning club finesse would provide enough tricks for game, but what if the club finesse lost? South quickly recognized the dangerous heart situation, and was grateful to have escaped a heart lead.
 
With the dangerous heart position in mind, and playing west for a likely king of clubs, South decided to try a deceptive play that has been around for many years. When East played his ♠J at trick one, south immediately won... but with  the spade ace! 
 
South next led his ♦4 to dummy's queen, and passed dummy's ♣10 to west's king. West, who had counted south's likely 18 or 19 points, and playing partner for the ♠Q that east "obviously" held, continued the attack with a small spade. 
 
It's hard to fault west's low spade return. What if south, as it appeared, held the ♥A and east held both major suit queens? Our deceptive south grabbed his queen and cashed ten tricks. 

South deserves credit for his gutsy deceptive play. But many well-oiled partnerships would probably avoid falling into south's trap. They might do so by employing either of two popular conventions - one that would occur during the bidding, or one that would occur during the play.
 
Fans of the Rosenkrantz Redouble could use that call as east in place of making a direct spade raise. Such action would promise a high spade honor - the ace, king or queen. So East's failure to redouble would effectively deny the spade queen. West would then almost surely shift to a heart.

Or the east-west partnership might have agreed to play some form of the Smith Echo. In this case, that convention would result in east playing his ♦2 on that second trick, discouraging a spade continuation by effectively denying the queen.  Knowing this, west would surely find that killing heart shift.
 
Few would suggest the Smith Echo be used by a casual player, and certainly not without extensive partnership discussion. On the other hand, the Rosenkrantz Redouble is easy to learn, and can simplify the defense against that ever-present contract of three notrump. It's also easy to recognize, since a natural strength-showing redouble by the advancer would rarely be possible. After all, there are still only 40 points in the deck!
 

♠   ♥   ♦   ♣