Wikipedia:Sandbox

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Introduction

With a 5521 – KQxxx and QJxxx in the long suits and nothing in the short ones – very few players will have doubts to intervene over her RHO opening in 1-suit, particularly if the partnership is using some convention for 2-suiter interventions. Then, why not opening that hand, if the opportunity arises, thus preventing the opponents from the privileged information exchange of their 1-suit opening? Because the partnership system does not have an opening bid telling partner that the hand may be a weak 5-5 2-suiter? There are several ways to do it, as presented at Chris Ryall Weak 2 Archive in the internet, or Tuomo Väliaho article in The Bridge World. Most of those treatments are exclusive to weak hands, therefore preempts, but that does not necessarily have to be the case.

F2s is a scheme of openings at the 2-level, where 2♦-2♥-2♠ indicate 2-suiters (5+/5+) and 2♣ is used as MULTICOLOR:

2♦: ♥ + any other suit

2♥: ♠ + minor

2♠: both minors

2♣: MULTICOLOR – weak-2 in a major, or balanced (major 5332 included) above 2NT, or powerful 1-suiter

2NT: balanced (major 5332 included), 20-22 hcp

Strength for the 2-suiters is a split-range: either 6-10 hcp (weak, 7 losing tricks or less), or 13-16 hcp (strong, 5 losing tricks or less). The intermediate range is open in 1-suit, as with 17+ hcp. Total frequency of occurrence is ~6 % (once every ~17 boards, in average).

Bidding continuations for the 2-suiters

With a weak or intermediate hand and at least 2 cards in the suit indicated by the opening transfer, responder should simply correct it. If (and only if) with a strong opening, opener will declare the second suit, or the shortest major (singleton or void) with the minors 2-suiter. So, responder has no need for trial bids with an intermediate hand with a fit in opener’s suit.

With a void or singleton in the transfer real suit and a weak or intermediate hand, responder may skip it, declaring the next one. With a weak opening and the second suit in responder’s bid, opener passes; otherwise declares the second suit economically. With a strong opening, however, opener will declare the second suit one level higher than with a weak hand, or the shortest major (singleton or void) with a minors 2-suiter. Again, no need for trial bids by responder.

With a good hand, with game prospects, responder relays with 2NT. With a weak hand, opener marks the second suit as economically as possible (bidding 3♥ with ♥+♠, 3♣ with ♣+♦). With a strong hand, opener bids the second suit at the 4 level (but 3♠ with ♥+♠), or the shortest major (singleton or void) with ♣+♦.

NB: With ♥+♠ (2♦ opening bid) and a weak opening, the rebid should be 3♥; with a strong opening, rebid is 3♠. With ♣+♦ (2♠ opening bid) and a weak opening, the rebid is 3♣; with a strong opening, rebid is in the shortest major.

Bidding continuation for the 2♣ MULTI

Responder has two possible relays, 2♦ and 2NT. Responder bidding ♥ or ♠ works the same way as after the ‘regular’ 2♦ MULTICOLOR.

Over the 2♦ relay, opener bids 2♥/2♠ with a weak-2, 2NT with the strong balanced hand (23-25 hcp), or 3 in the long suit of a powerful 1-suiter (4 losing tricks or less). If the partnership so desires, the powerful 1-suiter may be declared with a transfer at the 3-level (3♠ for ♣), immediately requesting key-card answers (step-wise).

Over the 2NT relay, rebids may be as if the MULTICOLOR had been done with 2♦. The powerful 1-suiter is declared at level 4 (naturally, not in transfer).

Bidding continuation for 2NT

The partnership will use their methods for the 2NT opening, but will keep in mind that the opener may have a 5332 in a major – therefore some sort of Puppet Stayman, or equivalent method, will be needed. The same applies in the case of a 2NT rebid after a 2♣ opening.

Dealing with interventions

If responder passes over an intervention, all subsequent rebids from opener will be strictly natural.

Responder’s 2NT over a suit intervention of her RHO, or DBL over a natural 2NT intervention, will be a relay, requesting opener to clarify the hand (in the same way as explained above).

Raising an opener’s suit will be merely preemptive, but a response in a different suit, not forcing, will show 5+ cards and a misfit if opener indicated some suit.

If an intervention occurs over responder’s bid, relay or otherwise, opener will only rebid with a strong hand, particularly with a 2-suiter.

As much as possible, rebids from opener will keep the meaning they would have if the intervention had not occurred.

2♦/2♥/2♠ openings in 4th position

Distributions are recommended to be the same as for the same openings in earlier positions. Strength for the 2-suiters, however, is recommended to be 10-13 hcp (7 losing tricks or less) or 17+ hcp (5 losing tricks or less).

Paulino M Corrêa, Lisboa, Portugal (2006)