Bidding systems generally define constructive opening bids in terms of just two things:
- The shape of the hand (ie. the lengths of each of the suits); and
- The overall strength of the hand.
Of course, by describing only these two things we are leaving out much of the detail of the hand, since we will not show anything about how the high cards are distributed amongst the suits. But because we have so few different opening bids to choose from, it is simply not possible describe that sort of detail.
Indeed, even when we restrict attention to shape and strength, there is only a very limited amount of information that we can convey with the opening bid. So we have to decide what is most important. And for unbalanced hands, it turns out that showing shape is most important. That is, while any opening bid will generally tell you something about strength (a standard opening bid might promise a minimum of about 12 points), your main concern should be to describe shape as effectively as possible.
The reason for this is that, according to the Think-Competitive principle, we have to anticipate what is going to happen in a competitive auction. And in competitive auctions, fit is all-important. This is most famously stated in the "Law of Total Tricks": if our side is bidding one suit and the opponents have bid another, then the decision as to whether to compete over an opponent's bid should depend almost entirely on how many cards we have in our suit and how many cards the opponents have in their suit. Strength hardly makes any difference to this decision (though of course it may be important if there are other decisions to be made, such as whether to bid a game). So if we are to get these competititive auctions right, it is vital that we know how good our fit is. In order to do that, we have to show shape.
When we hold an unbalanced hand, this increases the chance that we have a big fit - and also increases the chance that there will be a high-level competitive auction. Furthermore, if our side does have a big fit then it is likely to be in one of our long suits, and so it is essential that we tell partner which suits we have. This gives us our new principle: "Unbalanced-Hands-Show-Shape".
For one-bid hands, then, the situation is very simple: we have to try and describe the shape of the hand as well as possible with the opening bid. In this respect, opening bids which promise long suits are very good: a 5-card 1S opening is an excellent description of a hand which has five spades. The difficulty is in being able to give good descriptions for as many different types of hand as possible, and for one-bid hands this should be done on the assumption that we will only get one chance.
For two-bid hands things are more complicated. We must still try to show the shape of the hand, but now we are going to get two chances to do this. Perhaps this means that we do not need to worry about showing shape so much with the opening bid?
In fact this is unlikely to be true. It will usually take two shape-showing bids to describe the shape of an unbalanced hand well. For example if we hold a two-suiter, we need one bid to show the first suit and another to show the second suit. With a more flexible hand such as
we can show our long suit (spades) with the first bid and then hopefully double for take-out the next time (if opponents bid our short suit). Particularly with these flexible hands, a double is often by far the safest action in a high-level competitive auction, and so if we had not shown our long suit with the first bid, we would be struggling to show it later.
Occasionally, though, we come across a hand like this:
Suppose we start by showing shape on this hand with a 1S bid, and the opponents bid up to the 3-level or 4-level. This isn't a disaster, since the spade suit is easily good enough to rebid. But rebidding spades doesn't quite express how good this hand is. Look what happens instead if we are playing a strong club or multi-way club system and open this hand 1C. Again, the excellent spade suit means that we have a comfortable rebid even if the bidding comes back to us at a rather high level. But, having rebid 4S or whatever, we now feel that the hand is described perfectly: we have described the shape and the strength. So this particular sort of unbalanced hand - a strong major 1-suiter - is actually very good for strength-showing openings. This can be viewed as being an exception to the Unbalanced-Hands-Show-Shape principle, but really what is going on is that it is a pure two-bid hand and you know you will be able to show shape very precisely with your second bid. Note that a 1-suited hand with a long minor is not quite so good, because it may not be advisable to bid your suit on the next round if this would result in missing 3NT.