[Gerben42]

We'll meet a lot of weak NT pairs in the league next weekend, most of which are using transfers, so I thought it'd be worthwhile to look at some auctions.

(1NT*) p (2♦) p
(2♥ p (p) Dbl

* Weak

Considering that we already play a Dbl of 2♦ as TO of ♥, what is a delayed Dbl?

Penalty or "weaker than bidding earlier".

(1NT*) p (2♦) p
(2♥) p (p) 2NT

Natural?
Minors?
4♠ with longer minor?

(1NT*) p (2♦) p
(2♥) p (p) 3♥

Difference with a direct 3♥?
Difference with a direct 2♥?

[MFA]

I think you should seriously consider playing a direct double of a transfer after a weak NT as "values".

As late as Saturday, I had
Kxx, Axx, AQx, JTxx all vul.

(1NT 12-14) - pass - (2♦) - ?

X. This is not a hand where I'm dying to compete over 2♥, but if partner has some shape and/or strength, my hand is suddently very useful. Double and then selling to 2♥ felt perfect.

X & X strong takeout
X & 2NT strong natural
P & X limited takeout
P & 2NT twosuited
2♥ 5 spades+5minor.
Delayed actions weaker than direct actions.

[FrancesHinden]

I strongly agree with most of this.

Play double of a Stayman 2C or a transfer bid as showing a hand that would have doubled the opening 1NT (i.e. usually good 15+ balanced or semi-balanced). Otherwise you can be 28-high and completely stuck.

Rather an Michales, you can play an immediate 2H as a 3-suiter with singleton or void heart. Double-then-double is then a doubleton heart and is passable; you don't want to pass first as opener may well be about to break the transfer.

[Cascade]

I too play double of Stayman or a Transfer as showing values. Pretty much it shows a hand that would have doubled 1NT so around 15+.

The advantage of this is that it gets partner involved on marginal values. We play that the next double by either partner is takeout. Our agreement is that a subsequent third double would be penalties unless the opponents have bid and raised - and a free raise to 3Major is probably the most likely further competition after a transfer.

(1NT) Pass (2♦) Dbl
(2♥) Dbl

This shows a hand shortish in hearts with a few values - willing to compete opposite 15 or so.

(1NT) Pass (2♦) Dbl
(2♥) Pass (Pass) Dbl

This is also takeout.

This means that a delayed double after a pass is also takeout but with a weaker hand.

(1NT) Pass (2♦) Pass
(2♥) Pass (Pass) Dbl

Takeout around 11-14 hcp.

You also have an immediate bid of the opponent's suit available as some sort of takeout.

(1NT) Pass (2♦) 2♥

You could play this as the 11-14 takeout or perhaps a Michael's style bid or perhaps a stopper ask. Whatever you think is most useful? Guaranteeing the singleton heart as you suggest is a decent agreement.