[Ranmit]

Q regarding what is permissible under basic+ chart (lower level flights at NAP/GNT etc at the NABCs).

1. Are 'one under' good raises allowed (Ex: 1S 2H - showing good raise in S but not GF?)
2. Artificial 2NT opener showing 5-5 in 1 known + 1 unknown suit?
3. If playing strong club opening with 1D opening showing 12-15 pts with as few as 2 diamonds if balanced: an artificial 1H response to 1D showing 5-11 pts, need not say anything about hrts?
4. (Edited to add): Are there any restrictions on opener or responder's rebids? (I think not)

Thanks!

[johnu]

In my reading of the charts:

1. One under raise - Not allowed. Under allowable responses, this is not natural (1) and not game forcing (2). This would be allowed if it was a jump to the 3 level (or 2♠ over 1♥) (7).

2. 2NT showing a known and unknown suit - Not allowed. Under allowed opening bids, exception is if 2NT shows a very strong hand (7), or if 5-4 or better, both suits are known, average strength (8), or shows both minors (10)

3. 1♥ artificial response to 1♦ - Not allowed unless game forcing (2).

[Ranmit]

johnu, on 2025-August-02, 16:54, said:

In my reading of the charts:

1. One under raise - Not allowed. Under allowable responses, this is not natural (1) and not game forcing (2). This would be allowed if it was a jump to the 3 level (or 2♠ over 1♥) (7).

2. 2NT showing a known and unknown suit - Not allowed. Under allowed opening bids, exception is if 2NT shows a very strong hand (7), or if 5-4 or better, both suits are known, average strength (8), or shows both minors (10)

3. 1♥ artificial response to 1♦ - Not allowed unless game forcing (2).

Thanks. Also, are there any restrictions on opener's and responder's rebids? (I think not, but wanted to confirm).

[mycroft]

"Beginning with the Opening Bidder’s second call, all calls are allowed by both pairs."

And I don't read the chart at all differently from JohnU (except to add that transfer responses after 1suit-X are fine; but as he said, not legal if RHO passes or overcalls).

Note that your 2NT isn't legal on the Open Chart either, unless it guarantees Average values (Ro19). Two *known suits* is fine.