lycier, on 2016-February-21, 23:05, said:
I remembered a golden rule by Alan Trucott in the past, its general meaning is " Never bid twice with same value". Would you follow this bidding rule?
You try not to make multiple bids showing no extra information voluntarily, but sometimes partner has forced you to bid, and other considerations (more tightly defining the meaning of other bids) force you to make a low catchall default bid so that your other bids can be better defined.
Consider the problems with 1s-2d-3c being anywhere from 12-21 points still. Responder with a little extra may be unsure whether to just bid 3nt, or raise clubs and explore for a club slam. If opener can still have a 12 count, 3nt might be the last making game. But failure to raise might miss the slam, because after 1s-2d-3c-3nt, opener doesn't know if responder has 12/13 or 16/17, again 3nt might be the limit. That is why most good player require extra value for this type of "high reverse" sequence. Kokish actually recommend this high reverse show extra AND 5-5, and bid 2s waiting a lot.
Also consider the problems if 2nt doesn't promise stopper unbid suit. Does responder probe and expose yourself to lead directing double, or just bid 3nt and find off first 5-6 tricks when 4M on a 5-2 fit or 5m would have made? Or end up with 3nt down because the stopper is unprotected from the lead.
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I think these have violated this bidding rule, rebid-2♠ is little useful and inefficient, it is a waste .However I really don't know the principle of rebid-2♠,would you tell me? How to define 2♠,2N,3♣ and 3♠?
3
♠ jump rebid of opener's major is usually played as extra values and either no loser suit or solid missing ace (KQJTxx). Some relax the suit quality requirement. The advantage of play solid is that responder with singleton doesn't worry some other suit better, doesn't worry about multi trump loser if play slam. Disadvantage of play solid is that it make the bid rarely utilize, and sometimes come sequence like 1s-2d-2s-3c-3s-4s and no one know if other player have more than minimum opener and slam can potentially be missed.
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♣ show extra value (~15/16+), sometime also 5-5+
2nt is usually played as 12-14 or 18/19, with stoppers in the unbid. A minority, Bergen disciples, use 2nt as "catchall", not 6 spades, not suitable for high reverse. This has the advantage of having the 2M rebid promise 6 cds, but the disadvantage of stopper ambiguity and possibly ending in 3nt from the wrong side of the table. An even tinier minority, play things like "Shuler shift" where 2nt = 6+ spades, 2s = catchall, or "Martel shift" where 2H (being cheapest call by opener) = catchall, 2S = hearts (since your catchall replaced it).
2s is catchall (not suited other bids) if not playing something else as the catchall.
As for "inefficient", you have to consider the entire auction. Compare 1s-2d-3c, where 3c is 12-21, opener has shown spade + club, but still unlimited, vs. 1s-2d-2s-2nt-3c, where opener has also shown spade + club but now limited, and responder has also made a 2nd bid defining his hand better. More information has been exchanged and you are at the same level. Which is more efficient?
It's normal to bid 2nt as responder 2nd round a lot, not jump to 3nt. This allow further room opener describe hand. 3nt usually reserve for some extra value, 16-17, where you more likely to just make 3nt on power even opener shapely, and you want to show that extra value in case slam is there, but really don't have the 18-19+ you'd want to bid 2nt then 4nt.