[frank0]

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All of the bridge books about competitive bidding I have define 3♦ as single suit invitation but it seems like a mordern approach is treat this 3♦ as fit showing jump.

Could anyone tell me(or tell me where can I find) the detail of this convention? My questions include
1. What's the main purpose/advantage of this bid?
2. What's the rough strength/suit quality/trump qaulity of this bid?
3. Is this on if I jump to 4 level(partner simple overcall 2 level)? Is anything changes if responder enters the auction?

[Fluffy]

This is a fit jump if you are a passed hand because nothing else makes sense.

Fit jumps are a good description of your hand when you get them.

I use this bid as natural and forcing, because I play 2♦ as non forcing. But as a passed hand it is fit jump.

Raises to the 4 level are fit jumps, with more shape.

[Flem72]

The whole skinny -- and much more -- is at

http://www.bridge.is..._2054397795.pdf

a free download of Robson-Segal's award-winning book, "Partnership Bidding at Bridge." Go get 'em!

Regards and Happy Trails,

Scott Needham
Boulder, Colorado, USA

[mck4711]

3♦ so-called fit-jump:

Shows 4+trump-support and a good suit on its own. According to the author (Robson/ Segal: Partnership Bidding at Bridge, 1993) distribution is more important than strength, based on LOTT. The author calls it "the two way shot". Important term within this theory is ODR (offense defense ratio): The higher your offense strength in relation to your defense the more (higher/ more aggressive) you can (shall?) bid.
4♦ shows a hand with even more distributional features/ higher ODR.

Bids basically remain the same if RHO bids something, eg. raise; but minor adoptions.

You can download this book free from the internet as PDF. As a good complement I recommend Lawrence: Complete book on overcalls.

[frank0]

A very good source. Thanks for the link and suggestion.

[Zelandakh]

frank0, on 2011-October-10, 23:48, said:

All of the bridge books about competitive bidding I have define 3♦ as single suit invitation but it seems like a mordern approach is treat this 3♦ as fit showing jump.

Could anyone tell me(or tell me where can I find) the detail of this convention? My questions include

As has already been linked, Robson-Segal is an excellent read and has extensive details on jit jumps and much more.

frank0, on 2011-October-10, 23:48, said:

1. What's the main purpose/advantage of this bid?

The purpose is to get your hand type across in a single bid before the opponents can preempt you. The point is that while it is relatively easy to judge the level opposite a balanced raise, when the raiser has a strong side suit there is a strong danger of the hand being a double-fit. Whichever side discovers this first has a massive advantage in these auctions. Similarly, if the side suits represent a misfit you can judge to stay low and allow the opponents to misjudge by getting too high.

frank0, on 2011-October-10, 23:48, said:

2. What's the rough strength/suit quality/trump qaulity of this bid?

Most play that the fit jump shows 4 card support and a good 5 card suit on the side. Some only require an 8 card fit. At MPS especially some use the fit jump to suggest a lead rather than guaranteeing a real suit. I recommend starting with the first of these definitions and adjusting to suit your taste. As far as strength goes it is simplest to play that you only guarantee the offensive strength necessary to raise to the level (here the 3 level) of partner's suit. If you also play that a fit jump establishes a forcing pass then this has a knock-on effect as to the hand types that can bid them; this aspect of the agreement is also discussed in Robson-Segal.

frank0, on 2011-October-10, 23:48, said:

3. Is this on if I jump to 4 level(partner simple overcall 2 level)? Is anything changes if responder enters the auction?

Some play that a double jump is a fit jump that just shows extra offensive strength, some others play that a double jump is a splinter, thu allowing you to show both hand types. I prefer the former but both approaches have their advocates. Of particular importance is to decide if a bid of 4H is a fit jump (or splinter) after a spade overcall. Other jumps to game will normally be natural.

[gwnn]

You have a fit and you have a suit. Normally, in one round you can only show one of the two. If your opponents are kind enough to shut their pieholes for the rest of the auction, either showing the fit or your suit first is OK (provided that you know the general preference of your partnership). However, when your opponents are unkind (as they should be), it might get messy.

If you show only your suit, you will have an unpleasant guess whether or not you want to show your fit later. An example of such an annoying situation is (1S)-2H-(2S)-3D-(4S); p-??? what now? My partner knows nothing about my fit! but it's the 5 level already. too late. too bad! In fact I was kind of wrong in the previous paragraph, the consensus is that if you don't play fit jumps, showing your suit is generally considered to be inferior to showing your fit.

If you show only your fit, at least partner knows what is likely the most important feature of your hand, and he can bid on if he has extra length. However, we are now burying our secondary fit. And it's not that we want to play 5 diamonds instead of 4 spades, say, but his cards in our long suit are very good and his cards in the other two suits are not so good. If he has KJx x in the minors, he will be happy to double them if we fit jumped in clubs and happy to bid on if we fit jumped in diamonds.

Of course sometimes we want to look for slam instead of doubling them in game, and then the same considerations are relevant: how good his support is for our suit.

A corollary of all this is that you shouldn't fit jump on bad suits, say if you have

Axxx x Qxxxx KJx, of course you don't have a fit jump in diamonds any more partner will mis-evaluate diamond honours and will think that he solidifies our secondary fit when in fact we're quite far from running them.

[gwnn]

Read the first few pages of http://www.bridge.is..._2054397795.pdf it is a famous book by Robson/Segal, it has many fans on here, most people don't play everything from it (in particular, most people feel fit-non-jumps are dodgy), but their advocacy of fit jumps is very convincing.

edit: it's been linked here just a few replies above me, I wonder if my eyes suffer from some sort of quantum tunnelling too?

edit2: note that in the auction from the opening post high level bidding from opponents is just about impossible, so a fit jump is not imperative or anything. probably natural and forcing is a better use, honestly.

[TWO4BRIDGE]

Fit-jumps should be ON in competition whether partner is a passed hand or not.