[Knurdler]

A new partner has got me learning 2 way checkback (TWCB) and my job is to draft a simple agreement.
Do I need to say we play SAYC and Walsh style?
My questions are only on invitational sequences.

After 1m 1S 1NT 2C 2D, I am comfortable with responders third bids of: pass= to play in D; 2H = 4H (and hence 5s); 2S = 5S (denies 4H).
With 4H and 4H, responder would have started with 1H. What does 2NT show?

After 1m 1H 1NT 2C 2D, I am not so sure. Pass = to play in D; 2H = 5H and denies 4S seems reasonable. But is 2S = 4/4 or 5/4? What is 2NT?

Thanks

[DavidKok]

On either sequence 2NT is invitational and denies extra length in the majors, so four of the suit bid and at most three in the other one. There are two-way checkback schemes that use 2NT artificially, instead putting the no-extra-majors invite in 1m-1M; 1NT-2NT.
1m-1♥; 1NT-2♣; 2♦-2♥ shows 5(+) hearts and is not forcing. It does not promise or deny any particular spade length.
1m-1♥; 1NT-2♣; 2♦-2♠ shows 4-4 in the majors and is not forcing.
Some people play Reverse Flannery, using 1m-2♦ and/or 1m-2M to show hands with 5♥4♠ and particular strength ranges. This way your 2♥ rebid on the first sequence can deny a four card spade suit, and you won't end up in a possible 5-2 hearts fit with an undisclosed 4-4 spade fit. Alternatively you can decide to bid on as opener with 4♠2♥ on that sequence, but you will frequently end up playing 2NT.

[fuzzyquack]

2N depends on your other agreements, and it's an extra bid to add a meaning to. In particular, if 1m-1H/1N may show a balanced hand with 4S you may keep a bid for 4H4S invitational

[Knurdler]

Assuming a 2NT third bid by responder shows 4 of the bid major and 3 or less of the other one, how does this differ from raising openers 1NT to 2NT directly? (not invoking chechback).

[smerriman]

There isn't a "standard" answer to that question. Find something you're finding hard to show otherwise, and make it show that. Aside from artificial options like those mentioned above, I've seen people use one option to include support for opener's minor, and one to deny it.

[sfi]

The partnership with the most detailed notes in this area included the following agreements after 1♣/♦-1♥; 1NT:

• 2♠ = 4/4 in the majors invitational
  
• 2♣ - 2♦; 2♥ = 5+ hearts invitational
  
• 2♣ - 2♦; 2♠ = 5+ hearts, 4+ spades invitational
  
• 2♣ - 2♦; 2NT = 4 hearts invitational

2NT after the 1NT rebid was a puppet to 3♣, allowing us to sort out unbalanced two-suiters with support for opener. Maybe not optimal, but it was occasionally nice to distinguish between 5/4 and 4/4 hands in the majors.

[mycroft]

There really aren't a lot of full-response descriptions available (possibly in books I don't have, but I can't even find links to them online).

What is commonly played in my area is:

• 1x-1y; 1NT-2NT: clubs, opener assumes weak (similar to 1x-1M; 1NT-2M "to play"). For those 4-6 hands that would have gone weak 1NT-transfer to play in 3♣.
  
• 1x-1y; 1NT-2♣; 2♦-2NT: Invitational in NT.

To me this just sounds like "zero waiting to happen" - it never comes up, so is forgotten when it does. But it does make sense, and if it makes sense for your partnership, go for it.

In my preferred partnership, we play:

• 1x-1y; 1NT-2NT: Invitational in NT, 4-card y.
  
• 1x-1y; 1NT-2♣; 2♦-2NT: Invitational in NT, 5-card y.

Simple, stupid, clarifies the rest of the bidding (like what XYNT-2♣; 2-♦-2y means) and less likely to be forgotten (because it "feels like" a transfer INV auction). But the people who play the above method think exactly what I do, but backwards - why use two bids for one hand (2♣-2♦; 2y gets "treated as 5, will correct with 6" - note that means you're not one of those "rebid NT with singleton in partner's suit" pairs) when there's this awful hand you can't bid (which has never come up for me). So if that feels right for your partnership, do that. Or any of the other suggestions.

I do wish that someone of the Larry Cohen or Grant&Meckstroth reach would post something "standard" with explanations that could be pushed as the "expected default". Like several other conventions that are "critical, but dangerous traps" (Good-Bad 2NT is the one that comes to mind), "everybody knows how to play it, but nothing's written down, so 'everybody' could be playing it differently from their partner, or their opponents who can't explain either."

[akwoo]

Another option is that 1m-1M-1N-2c-2d-2N is invitational with values in the minor opened and 1m-1M-1N-2N is invitational without such values. This can help opener properly value HHxxx in their opening suit for the purposes of accepting an invitation.

[pescetom]

akwoo, on 2024-January-08, 23:44, said:

Another option is that 1m-1M-1N-2c-2d-2N is invitational with values in the minor opened and 1m-1M-1N-2N is invitational without such values. This can help opener properly value HHxxx in their opening suit for the purposes of accepting an invitation.

Another option is that 1m-1M-1N-2c-2d-2N is invitational to 3N and 1m-1M-1N-2N is a puppet to 3C over which responder can pass or show a GF+ two suiter. There are arguments for having more descriptive game forces rather than splitting hairs about invites.