At last night's team game at the club, Jenn made an amazing bid that won 9 IMPs for our team. With only our side vulnerable, she was dealt this in third seat:
I dealt and opened 2 Diamonds, a weak 2 bid, and her RHO passed. Now stop and consider this situation. We have 11 diamonds between us. Since I would not have bid 2 Diamonds in first seat with a 4-card major, the opponents must have a big double major suit fit with at least 9 spades and 8 hearts, and likely more. We have little defense against a major suit contract. LHO must have a big hand and will want to get into the auction.
The best result possible here is to buy the contract for 5 Diamonds undoubled. You don't expect to make it missing 3 aces, but it probably will only be down 1 or 2. If I had held these cards, I would have just bid 5 Diamonds, making RHO guess whether to come in at that level, but announcing our big fit. After this, we would run the risk of either being doubled or pushing the opponents into a makeable game, or, worse, slam.
Jenn found an ingenious way to achieve the ideal result. She decided to play a poker game with the opponents by bluffing strength. The best way to make a show of strength is to ask for aces. Now, it just so happens that Jenn and I play a convention which enables us to use a variation of RKC after partner's preempts that is an improvement over traditional Blackwood. It is often referred to as preemptive Gerber. So she bid 4 Clubs, which I alerted as our version of RKC. This had the intended effect of silencing LHO. I made the expected response, showing one keycard without the queen of trumps*, she rebid 5 Diamonds, and everyone passed. The two hands were:
We lost the 3 missing aces for down one, -100. Our teammates played it in 5 spades, making seven for +510, so the team was +410 for 9 IMPs.
* The responses to 4C are: 4D is no keycards (first step), 4H is one without the queen (second step), 4S is one with the queen (third step), 4NT is two without the queen, 5C is two with the queen, and 5D is the AKQ. If the opening preempt is 3C, then 4D becomes RKC for clubs and all responses are one step higher. (You don't want to use 4C over 3C as RKC, since it is better used as a continuation of the preempt.) This sometimes enables getting out at the 4-level when you don't have the cards for slam, which you cannot do using standard Blackwood.