[alibodin]

The bidding has gone on BBO in a friendly game, with no opposition bidding, the partnership is playing 5 card majors strong NT and ‘better’ minor so 1♦ shows 3+ and only 3 on 4=4=3=2 else its 4+

1♦ 1♠
2♣ 2♥


The partnership assumed it was natural; the opponents were surprised it was not self-alerted as 4SF.

The question is this 4SF?

How do people play this?

[Cyberyeti]

4SF to me

[mike777]

 Cyberyeti, on 2025-December-08, 08:10, said:

4SF to me

This,

[mw64ahw]

Not if you treated it as natural

[jillybean]

Most will play it as 4SGF, with a BBO Pickup partner I would not be sure

[P_Marlowe]

alibodin, on 2025-December-08, 06:57, said:

The bidding has gone on BBO in a friendly game, with no opposition bidding, the partnership is playing 5 card majors strong NT and ‘better’ minor so 1♦ shows 3+ and only 3 on 4=4=3=2 else its 4+

1♦ 1♠
2♣ 2♥


The partnership assumed it was natural; the opponents were surprised it was not self-alerted as 4SF.

The question is this 4SF?

How do people play this?

#1 It is FSF, this is the case since pre 1968 (Acol Land / Expert standard => Harrison-Gray)
The main reason is, that you need a way to ask p in a forcing manner, if he happens to hold
3 cards for responders major, if responder rebids his major, he is showing 6+ cards
Your seq. gets mentioned explicity in an article by Gray, ..., in case you are interested,
you may have a look at "Best of Gray", nice book.

This shows up more frequent, than the scenario, that responder has 54 in the major and is weak
and wants to play only 2H or 2S, playing 2S is still possible with 2H as FSF, but not 2H,
but see #2.

If you want to be able to have a bid, that enables responder to show the weak 2-suited
major hand, there are conventions ... look at Reverse Flannery

#2 How you play FSF is ..., there are 2 Variants the main variant is GF, some old diehards like me,
play it as inv.+, ..., there was also a variant to play it as exactly inv. ( I never understood this one ).
The inv.+ variant is Acol style, the GF variant is North Amercian ... but gained a lot of traction
in Europe.

#3 Just because it may be artifical, does not mean that the guy bidding 2H does not have 4+ hearts
The opener can raise the 4th suit to show 4 cards in the artificial suit, this is possible, if you
play FSF as GF

[helene_t]

Absolutely. This is one of the few sequences where FSF applies no matter what system you play.

You may agree that FSF does not apply
- after a 1♣ opening (because either the 1♣ opening, or the responses, are artificial)
- after a reverse
- after a 2/1
- After 1♥-1♠ (because you play Kaplan Inversion)
- when 2♣is available as XYZ

But in this particular sequence, as well as if responder's suit were spades, FSF certainly applies

[alibodin]

Thank you all I am convinced that it is 4SF, this is second time playing with this partner after a long break, (we played pre covid).

Thanks to P_Marlowe for your detailed reply most helpful.

I think if best to make 4SF GF.

[pescetom]

Just nitpicking about semantics and I basically agree with everyone else, but 4SF to my eyes is a natural assertion (the 4th suit is forcing), not a convention. What makes it a convention is playing that it may be artificial (semi-natural) and/or that it is forcing to game, which I suggest should be called 4SSN or 4SGF respectively.

[as an aside, there was a diatribe in Italy about whether/when 4SF which may be artificial should be alerted: the most eminent TD and lawmaker sentenced that it should not, as the 4th suit was the only remaining forcing bid and thus bidding it without the suit was a "natural convention". As a TD I reluctantly tow this line, but not if the agreement is game forcing too.]