[bluenikki]

1. Is redouble business? If so, what kind of club suit? I'm sure I told somewhere in the forum of my dumb double of a 2♦ transfer bid (fifty years ago in a relatively important match); redoubled making 4.

2. What kind of diamond suit justifies 2♦ instead of pass?

[DavidKok]

People play all sorts of different methods here. There is no universal answer on what to play.
Compared to a double of a Jacoby transfer, a double of Stayman is more complicated too. No suit has been singled out, and if we may want to play 2♣X (or maybe redoubled) then all four strains are in play.

A simple option is to ignore the double and bid as normal. This is not best, but has the advantage of avoiding big understandings. If sixth seat chooses to raise the clubs though, you may have to improvise.
A more complicated option is to show stoppers - bids as normal, while pass denies a club stopper and redouble can be something special (such as an offer to play). Responder can, if still interested, ask again by redoubling if opener passes. This has a benefit of giving some siding advantages in the major suits, but can lead to confusion if responder chooses not to repeat the question but instead wants the lead up to them.
There are other popular schemes too, so unfortunately you'll have to pick one and stick with it.

[johnu]

bluenikki, on 2026-January-17, 14:31, said:

1. Is redouble business? If so, what kind of club suit?

I play redouble as clubs and suggests playing the redoubled contract. This occurred a few years ago. I had ♣AQ108 and redoubled. Partner had a doubleton club, and a 3NT invitational type hand. 2♣ redoubled making 3 for a top board. The 2♣ bidder went away muttering that he shouldn't have doubled.

[apollo1201]

I play that XX is business too. The rest of the « system »:
- 2D: decent 5 (or 6😁😁)-cd suit, no M, no C stopper
- 2M: that M and wants to play the hand (so a C stopper)
- 2NT: no M, C well stopped
- 3C: both M

Otherwise pass, then if resp XXes to re-ask, 2M = the other M to make resp declarer in a M contract and protect their potential C holding on the lead.

Similar for transfer being Xed except that resp can be broke so playing 2XX is risky so is no longer business:
- XX: 3-cd fit, no stopper (resp plays the hand)
- 2M: 3-cd fit and desire to have the lead
- 3M-1: 4-cd and not min, no stop
- 3M: 4-cd and not min, wants to play

Pass is 2-cd and resp can re transfer with XX if they do not want to play.

One could wonder what to do with Ax(x) in the Xed suit, pretending not to stop or declare.

[bluenikki]

apollo1201, on 2026-January-18, 16:56, said:

Similar for transfer being Xed except that resp can be broke

Stayman responder can be broke also. That's why the auction after ... (Dbl) - P - (P) - ? needs discussion.