[Bbradley62]

In the first of the two following hands, South's double is a support double, but in the second it is not. Are support doubles only on opposite partner's major suit bid?

Stephen Tu, on 2013-April-02, 16:36, said:

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[ArtK78]

That is a matter of partnership agreement, but the mainstream approach is that support doubles only apply when the response is a major suit.

I have one partner who plays support doubles over 1♣ - (P) - 1♦ - (1M).

[georgi]

Maybe Eric Rodwell didn't considered 1♣ - p - 1♦ in it

[georgi]

Copied from - Support Double

Bidding Sequence 5*:
S - W - N - E
1♣ Pass 1♦ 1♠
Double

5*: This particular auction, whereby both Minor suits have been bid by the partnership, may also become ambiguous since it is not clear whether the double of the opening bidder signifies a Support Double or a Negative Double showing a 4-card Heart suit. Again, a solid partnership agreement is necessary, especially for this particular bidding sequence.

[Bbradley62]

georgi, on 2013-December-09, 09:12, said:

Copied from - Support Double

Bidding Sequence 5*:
S - W - N - E
1♣ Pass 1♦ 1♠
Double

5*: This particular auction, whereby both Minor suits have been bid by the partnership, may also become ambiguous since it is not clear whether the double of the opening bidder signifies a Support Double or a Negative Double showing a 4-card Heart suit. Again, a solid partnership agreement is necessary, especially for this particular bidding sequence.

I was not asking how "the book" says it should be played, or how I might want to play it with my regular partner; I was asking how GIB plays it.

Unfortunately, one of the hands in my original post was a link to myhands, which is now gone. However, today I encountered a hand that was the opposite of what had been my understanding. The auction was 1♣-(p)-1♦-(2♣, natural) back to me. Mousing over my options showed that a double here would be a support double, which surprised me. So, can we get a full explanation of when support doubles are on in the GIB bidding system?

[georgi]

Currently for GIB Double by opener is always SuppX once responder could rebid his suit on level 2.

That includes also

1♣ - p - 1♦ - 2♣
X

( case where it's some cuebid like 1♥ - p - 1♠ - 2♥ is not SuppX as 1♥ shows 100% 5+ cards )

Of course, it's specific case when 4th seat overcall matches opening (rather minor overcall).

It will be discussed but also should be taken in account when you have:

4M333 shape while opening 1♣ where 4th is not partner's suit.

So what would you like to do here?

Opening 1♦ is kind of easier as you are no longer 4M333, but could have 4♦333 or 4♦4♣ 3rd in partner's major and 2nd in OM.

And once you pass such overcall with some 4333 or 4432 trying to avoid misinterpretation by partner you will break the sequence and won't be easy to describe hand.

If you find partner with 5332 and 7-8HCP, could he reopen with double or to reopen with 2M?

However, it seems that by opening 1minor it's more likely to have support 3 cards than 5+ and opponent overcalling in same suit and overriding SupX meaning to be profitable.