Notrump openings and rebids
An opening bid of 1NT or 2NT shows a balanced hand (“standard” would be 15-17 and 20-21 respectively), but neither promises all suits stopped.
Opener’s 1NT or jump-to-2NT rebid also show balanced hands (12-14 and 18-19, respectively) but also don’t promise stoppers in all suits. For example:
I would rebid 1NT after 1-1 with, say
I would rebid 2NT after 1-1 with, say:
In a 2/1 GF auction, I prefer to allow opener to rebid 2NT with a flat hand, but not everything stopped.
I would rebid 2NT after 1-2 with, say:
I would not rebid 2NT with a small doubleton in an unbid suit, preferring to raise partner with 3 trumps if need be.
A response of 1NT to 1 or 1 says nothing about stoppers. Responder might have several suits unstopped.
For example, I would respond 1NT to 1 with, say:
But, if the opponents overcall, responder’s 1NT shows a stopper(s) in their suit.
For example: 1 (1) bid 1NT with:
A response of 1NT to 1 or 1 (by partnership agreement, possibly “forcing” or “semiforcing”) says nothing about stoppers. Again, if the opponents overcall (such as 1 after 1), the 1NT response shows a stopper(s) in their suit.
1 P 1NT with:
1 (1) 1NT with:
Assuming it isn’t conventional (like Jacoby 2NT), a response of 2NT would tend to show the unbid suits stopped. If there is an overcall, then 2NT definitely shows their suit stopped.
1 P 2NT with:
1 (2) 2NT with:
This should show a stopper(s) in all unbid suits (and definitely so after an overcall).
1 P 3NT with:
1 (1) 3NT with:
If our side has bid two suits, natural bids in notrump tend to show stoppers in the unbid suits (but not guaranteed). If the opponents have bid a suit, then the notrump bidder is assumed to have that suit stopped. If stuck, you might have to bid 3NT naturally with an unbid suit(s) completely unstopped, such as:
1 (3) 3NT with:
Or, (3) 3NT with:
If your side has bid 3 suits, a notrump bid should deliver a stopper in the 4th suit. For example, after 1-1-2, a heart stopper would be expected for a notrump bid.
If the auction gets complicated, assume that the notrump bidder always has the opponent’s suit stopped. If he doesn’t, he shouldn’t bid notrump (sometimes a cuebid, often called a “Western cuebid,” can be used).
Conventional notrump bids (such as Unusual notrump, Jacoby 2NT) obviously say nothing about stoppers (nor anything about notrump shape).
For more, try this quiz.