Source: https://www.andrewrobson.co.uk

Sometimes – often – you can gain more by penalising the opponents than by making your own contract. This is particularly true when an opponent has opened 1 NT. Any hand, balanced or otherwise, with sixteen or more points should double 1 NT. This is a “Penalty” double and unless partner is particularly weak with a long suit (in which case he will remove the double) he is expected to Pass.

The carnage can be horrific, especially when the doubler has a long suit to lead…

Dealer South Both Vul

9 7 5 4
K J 4
9 7 6
Q 10 8
A Q
6 2
A K Q J 4 2
7 5 4
8 6 3 2
A Q 10 8 3
8
6 3 2
K J 10
9 7 5
10 5 3
A K J 9
West North East South
1NT
Dbl Pass Pass Pass

There are those who would claim that South should not open 1 NT (12-14), as he holds two suits unstopped. I am not one of them – a 1 NT opener is by far the most descriptive opening bid and only occasionally results in trouble.

West led  A and played out all his five remaining s, East discarding 2, 3, 6 and 2, ♣. By throwing low cards in the suits he didn’t want, East signalled for s whilst retaining all five of them. West switched to 6 to J and Q, and East accurately returned 8. West beat declarer’s 10 with Q. He cashed A and led 2. East beat dummy’s 4 with 10, cashed A felling dummy’s K, and took the last two tricks with 8 3.

Declarer had not made a single trick, losing 2000 points. Rather better for East-West than bidding and making their own contract!

THE RULE OF SIXTEEN: If an opponent opens 1 NT and you have sixteen + points, you must double – a penalty double.