The Cappelletti convention is a very popular convention for interference over the opponent's 1 no trump opening. The convention's biggest advantage is that the double is used as penalty therefore making it effective against weak no trump openings too.
|X||Penalty, at least 15 good points or (6) 7 tricks.|
|2♣||2♣ shows any single suited constructive hand, 8-15 points, 6 or very good 5 card suit, or a stronger hand, not suitable for penalty double. A jump in the suit on the three level will show the stronger kind of hand.|
|2♦||2♦ overcall shows both majors, at least 5-5 in vulnerable and at least 5-4 in non-vulnerable. Strong hands with 4441 or 4450 can also be bid through 2♦ if they are not suited for a penalty double.|
|2♥||5♥ + (4)5 minor hand, respectively to the vulnerability, no more than 7 losers in green and no more than 6 losers in red.|
|2♠||5♠ + (4)5 minor hand, no more than 7 losers in green and no more than 6 losers in red.|
|2NT||2NT is either ♣ + ♦ constructive hand or any two-suiter strong hand. With the strong two-suiter a second bid should be bid after partner tries to sign-off in a minor.|
|3♣/3♦/3♥/3♠||Normal preemptive bids.|
After partner's penalty double
Most importantly, we have to ask the opponents, whether their pass is forcing or a not, considering, that many players play pass to ask for redouble which gives them more bidding space when escaping.
If pass is forcing, we don't have to escape from 1NT immediately with weak hands, because opener has to redouble, and we have time to escape later. Therefore new suits in level 2 are non forcing constructive hands, 2NT is GF Stayman and new suits in level 3 are GF and natural.
If pass is natural and passable we have to be careful. The best solution is to act accordingly to these guidelines:
- Pass with 5+ points or more with semibalanced hand hoping to defeat 1NT
- Pass with very weak but balanced hands, hoping that either partner alone can defeat the contract or that any 2-level contract we would play would be way more expensive than the 1NT doubled making. If we take 6 tricks in 1NT they score 180, if they take 7 against us on the two-level it's 300 or 500 for them
- Bid on the two level with weak unbalanced hands
- Bid 2NT or on the 3-level with strong unbalanced hands. 2NT is Stayman, new suits on the 3rd level are natural and game forcing
After partner's overcall
Over 1NT-2♣ showing a single suited hand we should normally bid 2♦ as a relay asking for partner's suit. With stronger hands we should use the 2NT relay to ask partner to describe his hand.
|3X||Weak hand with the suit bid|
|3NT||Strong hand with a minor suit. Remember that partner can have ♣ too if he wanted to bid 3♣ over our 2♦ bid.|
|4♣/4♦||Strong hand with ♣/♦. These hands are too unbalanced to bid 3NT you should treat them like so.|
|4♥/4♠||Strong hand with ♥/♠.|
Similarly the 2NT relay can be used after partner's 2♦ overcall showing majors.
|3♣||5♥ + 4♠ unlimited, to that responder bids the prefered major with invitational hands|
|3♦||5♠ + 4♥ unlimited, to that responder bids the prefered major with invitational hands|
|3♥||5♥ + 5♠ weak|
|3♠||5♥ + 5♠ strong, GF|
|3NT||4♥ +4♠ + 4-5 in a minor suit, strong hand (15+), we could not double with unbalanced hand|
Finally the easiest is when partner bids 2♥ or 2♠ showing that major and an unknown minor side suit. The important thing here is that we should be able to sign off in partner's minor suit, so the 3♣ bid is used as artificial "Pass or correct". With at least invitational hands the 2NT relay can be used.
|3♣||5♥ + (4)5 ♣, weak hand|
|3♦||5♥ + (4)5 ♦, weak hand|
|3♥||5♥ + 5 ♣, strong hand|
|3♠||5♥ + 5 ♦, strong hand|
Although the 2NT invitational relay is mainly for when 1NT was a weak notrump, which is any no-trump that can contain a hand with 13 HCP or less by definition. As now days players playing strong no trump openings tend to open weaker offshaped hands with a good minor suit with 1NT too, bidding a game becomes more and more an option against strong NT as well.