[pilun]

1♣ - (4♥) - X

How do people play this double?
(I'm assuming vulnerability and form of scoring make no difference.)

Is it "transferable values" and what does that mean?
Balanced-ish with a couple of cover cards? How strong?

Is it takeout, so maybe a 4-1-4-4 7-count?

Is it a penalty suggestion, so a likely trump trick plus a bit outside?
Opener needs great shape to remove.

Given the auction and your agreements, what should opener do with

♠T6 ♥A5 ♦AQT3 ♣AQJ54 ?

Would vul and scoring affect your answer?

TIA

[DavidKok]

Sorry to be blunt, I feel like you are asking the wrong question.

For me this is a takeout double, but I'm sure people play it different ways. Personally I feel strongly that assigning a different meaning to this double is worse. However, it is important to understand what 'takeout' means. The general meaning of a takeout double is not 'three-suited with shortage in their suit', though it often overlaps. It is 'I want to enter the auction but have no good bid. Partner, you decide'.
In particular, the exact meaning is defined almost entirely through negative inference. At low level (say, 1♣-(1♥)-?), most hands have some other descriptive bid. Consequently the 'have no good bid' hands are fairly limited, and a takeout double is very descriptive. What's more, as the level of the auction is low, opener's best course of action is almost always going to be to take the takeout double out to some other strain - we rarely want to defend doubled at the 1-level, and looking for a fit at the 2-level is low risk. However, as the auction gets higher, the odds shift in two ways. Firstly, bidding is more committal, taking a large risk (we need to make a high level contract) and letting the opponents off the hook (we give up the opportunity to defend a high level contract). Secondly, the odds that defending is sufficiently profitable, maybe even best, go up significantly if the opponents bid more. Both of these lead to overloading the takeout double (there are more hands that 'have no good bid' because they are not sure if we want to play, but also 'want to enter the auction' as it seems to be our hand) as well as to leaving it in for penalties more often.

A partnership needs to make an agreement about doubles after high level preemptive action within this context. If you play 'penalty-oriented', responder has to pass with the most frequent hands - those with relative shortage in hearts and a smattering of outside values. If you play 'takeout' partner should not double with a stack in hearts, but can enter with many ambiguous hands that want to invite opener to think again. 'Convertible values' is something in between, but in my experience is often poorly defined.

Either way, opener tends to need some good shape to remove. Bidding at the 5-level contracts for about 19 total tricks (we want to make 11 and if 4♥X goes off more than 2 we won't gain much, if at all, from sticking our neck out), so usually we need either ourself or partner to have some pretty wild shape to go there. Partner's takeout double denies the ability to make a commital decisive bid, and we should play partner for a not-too-wild hand. One nice advantage of the strong club in competition (yes, really. There aren't many, but this is one) is that responder can force to game with as little as 8 HCP or equivalent playing strength, and a bit less even under pressure, so responder can enter the auction on a much wider range of hands than in a standard competitive auction. This helps the partnership catch up after the lack of shape communication from opener's 1♣.

With my agreements above I would pass as opener. I think 5m and even a slam might well make some of the time, but I have no space left to explore it. I hope that if partner has a very impressive hand they would have taken unilateral action, and I do have some detailed agreements over 4♥ to help with this, so I think the odds favour defending. If partner has ♠AKxx, ♥x, ♦Jxx, ♣Kxxxx and I just missed a grand (on a winning diamond finesse) I will take solace in the fact that we seem to have 6-8 defensive tricks.

[pilun]

4NT has some appeal with this particular shape, though you would need the understanding that partner always bids 5♣ with 3-3 or 2-2.
This as compared with 2-2-5-4, when you could play the 4-3 club fit rather than 5-3 diamond fit. Doh!
Whether you bid or pass depends on the expected ODR for the double.

A 4-1-4-4 7-count with an ace and a king will make 5m. (Okay 4♥ rates to be 2-off but 1-off would not surprise.)

♠KQxx ♥Kxx ♦xxxx ♣xx

will want to double too. The partnership needs an default style, prepared to pay out.
If "takeout doubles are for takeout" responder might want to double with

♠xxxx ♥-- ♦Kxxx ♣Kxxxx,

when -590 would not surprise.

I have no strong view, just interested ion what players expect for double.

[DavidKok]

If you've already made up your mind there is very little point in asking.