The ACBL and Suction
Nature is not alone in its abhorrence of vacuums. In 1998, the ACBL amended the section of the General Convention Chart which relates to No Trump defenses by requiring that direct overcalls "other than double and 2C, must have at least one known suit." This change endorsed virtually all popular overcall systems (e.g. Cappelletti, DONT, Brozel, Astro, or Ripstra) while prohibiting our favorite; Suction. Suction is unique among overcall systems in that it combines one-suited and two-suited hands in the same overcalls.
For those not familiar with Suction, it is a two-edged sword that removes uncertainty for the overcalling side while simultaneously introducing ambiguity in the opponents' method of coping with interference. It accomplishes this while maintaining the ability to describe all one- and two-suited hands.
In describing two-suited hands, Suction avoids the use of bids such as "Clubs and a higher suit" or "Spades and a minor." An Advancer, facing a poor fit for the known suit after an overcall of this type, has Hobsen's choice of potentially leaping from the frying pan into the fire or remaining fixed by his system. Inquiring only when holding support for the remaining suits will miss many opportunities to improve the contract, a disadvantage at any form of scoring but particularly costly at matchpoints if a major-suit fit lies undiscovered.
The Basics of Suction
Suction uses a suit overcall to show either a one-suited hand in the suit immediately above the overcall or a two-suited hand in the touching suits beginning two ranks above. For example, a 2C overcall of 1NT would show either a one-suiter in Diamonds or a two-suiter in the majors.
The only suit combinations left unshown by the basic structure are the non-touching two-suiters in Clubs/Hearts and Diamonds/Spades. These are commonly shown by Double and 2NT, respectively. A Suction variant reverses the meaning of the 2S and the 2NT overcalls. This permits Advancer to show a preference for Spades at the two-level when Overcaller shows a two-suiter in Diamonds and Spades.
In the case of the combination overcalls (showing the one- or two-suiters described above), Advancer relays by bidding the next higher suit. Overcaller can then Pass to show the one-suiter (gaining the additional advantages of transferring the hand so that Advancer's hand remains closed during the play as well as placing the strong hand on lead) or bid the next suit up the line, showing the two-suiter. Advancer then Passes, corrects, or raises to an appropriate level.
No doubt, the reason for the preferential treatment shown to every No Trump overcall system other than Suction was the the difficulty it creates with its initial ambiguity. The lack of an anchor suit both deprives Responder of the ability to cue and of the opportunity to show or deny stoppers. While passing with the intent to initiate Lebensohl once Overcaller's hand is defined is an option for Responder, such a strategy permits the opponents free reign to describe their hands and the 2NT relay may no longer be available by the time the auction returns.
A disadvantage to Suction (aside from its current banishment) is its lack of efficiency in certain situations. There are eight occasions where either a one-suiter is shown at the three-level or a preference may be taken at that level, including two occasions involving major suits. Swapping the 2S and 2NT overcalls, as mentioned above, improves matters a bit.
Although the change to the General Convention Chart may have outlawed the Suction convention in the direct seat, it has not made it impossible to use a No Trump defense which combines one- and two-suited hands in the same overcall. While the new restriction requires the presence of at least one known suit, it remains permissible to introduce ambiguity as to the presence of a second suit.
We call this system Preferences, although nominations for a better name are open. The underlying thread is that all suit overcalls show either a two-suiter in the touching suits immediately above the overcall or a one-suiter in the higher of those two suits. As an illustration, an overcall of Two Diamonds shows either a two suited hand in the majors or a one-suited hand in Spades. This complies with the GCC mandate, as Overcaller is known to have Spades in either instance.
The basic structure is:
Assuming initially a two-suiter, Advancer takes a preference. Overcaller can then Pass with either hand type when Advancer chooses the higher suit, or correct when he holds the one-suiter and Advancer has shown a preference for the lower suit. With no preference between the two suits, Advancer should probably show a preference for the known suit as this not only allows the ambiguity of Overcaller's holdings to continue through the auction, but also gains the transfer and lead advantages described earlier.
The efficiency of this basic structure can be improved by treating Double as the suit below Clubs. This permits the Double to take over for the 2S overcall, allowing a hand with both minors or a Diamond one-suiter to be shown at the two-level. The trade-off of being able to stop at the two-level when holding the minors is offset by the lessening of the disruptive value of replacing the 2S bid, as most pairs simply bid right through an intervening Double. Each partnership will need to determine which approach it wishes to use.
After this switch, the structure is now:
As in Suction, the only two suit combinations left unshown by the basic structure are the non-touching two-suiters. The Double is also used to show the Clubs/Hearts and Diamonds/Spades combinations as the GCC does not require a known suit for the Double. After this addition, the Double now indicates either:
C&D or D or C&H or D&S
It may look confusing, but it is simple to use. As normal, Advancer assumes that Overcaller holds both Clubs and Diamonds and takes a preference between them. If Overcaller has the long Diamond hand and Advancer shows a preference for Clubs, Overcaller corrects to 2D. When Overcaller holds the other hand types (the non-touching two-suiters), he corrects the preference to the major that he holds, thereby showing that major and the unmatched minor.
If a partnership leaves 2S with its original meaning, then the Double shows only the non-touching two suiters. If this option is used, Advancer indicates a preference on the assumption that Overcaller holds Clubs and Hearts. Overcaller either Passes the preference when holding Clubs and Hearts, or bids the next higher suit to show the Diamond/Spade two-suiter. Advancer then Passes or corrects as appropriate.
For completeness, a partnership may wish to define a Double followed by a pull to No Trump at the lowest level as showing the big balanced hand for those occasions that the bridge gods deal a balanced 20 count and an opponent has the temerity to open a weak No Trump. This treatment is applicable to Suction as well, humorously termed "Kirby" due to the strength of the vacuum.
Preferences leaves overcalls of 2S (if you adopt the expanded Double principle) and 2NT undefined. As all one- and two-suited hands types are already shown, these bids may be used to describe three-suiters: 2S shows any three-suiter with Spades, and 2NT a three-suiter without Spades, specifically 1444 (or no Spades). A suggested follow-up to the 2S bid would be 2NT to ask for Hearts; 3C denying, and 3D promising Hearts so that the transfer advantages can still be had.
As a Club one-suiter will always be played at a minimum of 3C, and the 3C overcall is unspecified in Preferences, a partnership may choose to bid 3C directly when holding a Club one-suiter for its increased preemptive effect. If Preferences is used in the balancing seat, this treatment ensures that the strong opponent is placed on opening lead.
Preferences retains many of the advantages of the Suction structure. The opening side faces ambiguity after every overcall, yet the overcalling side has the information its needs to take a preference and place the final contract without having to face the quandary sometimes createed by overcalls which fail to specify the second suit.
What was a disadvantage of Suction, its number of three-level conversions, is a strength of Preferences. By replacing the relay structure with a preference structure and loading the Double as described, the number of times Advancer's preference may result in a three level contract is reduced to four, none of which involves bidding a major at the three level. Those four occasions are the preference to either minor when held with the unmatched major, Clubs when Overcaller has a Club one-suiter, and Clubs when Overcaller holds the blacks.
In comparison, Cappelletti has seven such occurrences. DONT, arguably, never requires a three-level preference, but it does so as the expense of five "frying pan" combinations which either require Advancer to hold his peace in the face of an ambiguous bid or risk a return to Overcaller's initial suit at the three-level and telegraphing a misfit to the opponents.
Given this system's efficiency in two-level preferences, a partnership has wider latitude in overcalling with lighter values or adverse vulnerabilities. This also makes it more viable than other systems for use over natural 2NT and 3NT openings.
At present, there are no ACBL General Chart prohibitions on conventional calls in the balancing seat following a 1NT opening. Feel free to adapt this system for use in balancing as well.
Given the value of a balancing seat Double, a partnership may wish the "unload" the Double, having the 2S overcall retain its original meaning (C&D or long D) and use 2NT to show the untouching two-suiters. After a balancing 2NT showing the untouching two suiters, Advancer indicates a preference on the assumption that Overcaller holds Clubs and Hearts. Overcaller passes with that combination, or corrects the preference to the next higher suit with Diamonds and Hearts, which Advancer passes or corrects. As an alternative, those who are unwilling to let the ACBL have the final word, may continue to use Suction for balancing situations.