Friday, 4 January 2008

Interference over Natural Suit Openings

There is an old debate about whether a new suit by responder (e.g. 1S : (2C) : 2H) should be forcing or not. Either method is very useful when the appropriate hand type comes up - and causes difficult problems when you pick up a hand of the opposite type. If forced to choose one or the other throughout, I would prefer to play a new suit as forcing (which is standard in most parts of the world). Though non-forcing free bids do look very attractive when the suit is a major that can be shown at the 2-level.

But there is no need to choose. By using artificial tricks such as transfers we can usually show both hand types at an appropriate level. Unfortunately, different situations require different gadgets. Below are the methods I'm currently using for 2-level interference over 1D/1H/1S openings, which demonstrate all the various ideas that might be used.

1. Over a 2C overcall.

Here we use switch: that is, of the two unbid suits, a bid in one of them shows length in the other one. So:

Over 1D : (2C), 2H shows spades and 2S shows hearts.
Over 1H : (2C), 2D shows spades and 2S shows diamonds.
Over 1S : (2C), 2D shows hearts and 2H shows diamonds.

This essentially gives us both a forcing and a non-forcing bid in the higher-ranking suit, while not raising the level on the lower-ranking suit.

Note that the "switch" relies on both unbid suits being at the same level. So if you are fond of this method you could use it over spade overcalls as well, and also over 1S : (2H) and suchlike. But we actually do different things there.

2. Over 1M : (2D)

Here we free up some space by giving 2NT an artificial meaning. This allows for the following structure:

A bid of 2 of the other major is natural and not forcing.
2NT shows clubs.
3C shows the other major (stronger than the NFB).

3. Over 1D : (2M)

Again it makes sense to use 2NT as a transfer to clubs here. Unfortunately this time there is a real shortage of space, since while we would like to use 3C to show the other major, it would also be nice to have a way to show a good diamond raise below 3D. We can't realistically do both.

I currently play 3C as the diamond raise, so over 1D : (2S) we have to play 3H the traditional way, natural and forcing. Over 1D : (2H) we have 2S as a NFB and 3H showing a stronger hand with spades.

4. Over 1M : (2OM)

This is where transfers really come into their own. Again starting from 2NT we can play

2NT shows clubs
3C shows diamonds
3D is a raise. (When we have two artificial raises available below 3M, as with 1S : (2H) : 3D/3H, we use them to distinguish between 3- and 4-card support.)

Exactly the same transfers work if opponents bid 2M Michaels over our 1M opening.

5 comments:

NickToll said...

Welcome back, David.

What is your opinion about playing Rubensohl in all of those sequences, for sake of simplicity? You will not get the best of the world in each single case, but the accuracy-vs-complexity ratio is acceptable... or is it not?

DavidC said...

Well, you do end up with some unusual meanings, like

1D (2S) 3D

not being natural. If you don't mind this sort of thing it should be OK.

Paul said...

How weak can 1♠ (2♦) 2♥ be when it is non-forcing?

DavidC said...

I would say it's a constructive bid. From opener's point of view I would be imagining partner having maybe 7-9 HCP as a typical hand. But it could easily be less if it looks important to get the suit in. You'd be looking at your holdings in the suits already bid, as well as wanting good hearts.

Martin Carpenter said...

Interesting.

A couple of notes:
(1) I suppose that with switch you negative double with 4 higher suit, 5 lower suit shape (4S5H after 1D - (2C) say).
Otherwise you've made finding the 4-4 fits quite clumsy.

(2) iirc in the Useful space principle (a small booklet of bridge world articles which talks about this stuff and other things) Rubens doesn't like the idea using this kind of transfer 2NT bid in minor suit auctions.
(here after our 1D opening)

For one thing 2NT is needed much more of course but you'll also do nasty things to some potential 3NT's by using 2NT to show clubs.