Dear Ed and Peter,

In IMP scoring, neither side vulnerable, I held as South:

¹ Can be a four-card suit with as few as 10 points

Thanks,
Bill Yu

Reply Ed Hoogenkamp (South)

Dear Bill,

In my experience the best approach is to assume the 1♠ opening to be on a five-card suit, even if it can be made on a four-card suit. After all, even if you can open 1♠ on a mere four-card suit, it rarely happens: you only do so if your distribution is 4-3-3-3.

My choice (in your system) would definitely be to bid 2♣, Drury. The big advantage is that the bidding is clear and we are in good shape to find the best contract.
And even in the rare case that partner has only a four-card spade suit, this deal probably plays quite well in 4♠ in the 4-3 fit, since partner is bound to have three-card club support then (4-3-3-3, remember?).

Before you put down dummy you should take one precaution though: add the ♣3 to the spades. Next some acting comes into it: show surprise when partner observes there is a club in your spade suit.

Peter sometimes puts a diamond between his spades. A lot less convincing, I must say.

Saludos desde Bracelona.
 

Reply Peter van der Linden (North)

Dear Bill,

For visitors who are unfamiliar with Drury I will give a short treatise on this convention: it enables responder to show support after partner has opened a major suit third in hand (most pairs have agreed upon the convention after an opening fourth in hand as well). An example:

Since an opening in third seat can be substantially weaker than an opening in the first or second (and fourth...) hand, South is in a fix. Assuming he plays normal double raises (invitational) he is strong enough to do so if he can be sure that his partner has at least normal opening strength (12⁺).
But after partner has opened third in hand on possibly as little as 8-9 HCP, a double raise may result in 3♠ down one. On the other hand, a cautious raise to 2♠ may result in 2♠+2 if partner has a decent 14-15 count...
Drury solves this problem: South responds 2♣, showing spade support and 10⁺ points (including distributional points; of course he has fewer than 12 HCP since he has already passed).
In classical Drury the opener shows sub-standard opening strength by way of a 2♦ rebid.
In reverse Drury he does so by rebidding his opening suit at the minimum level.

Now to your problem. Firstly I don't recommend opening fourth in hand on a mere 10 count and four spades. I would pass such a hand. The Rule of 15 works well, if you are considering whether or not to open fourth in hand: 'Open, if your combined number of spades and HCP is 15 or higher, pass when it is lower'. The idea is that if you have the spade suit, your side is more likely to win the bidding. Ending up in 2♠ is quite common. If you have hearts instead of spades, the opponents are therefore rather likely to win the bidding at 2♠ instead of letting you play 2♥. 

Still, if your partner has 11 HCP and four spades, he can open 1♠ and your question applies. I agree with Ed that assuming that partner has five spades is the most practical solution.
If he turns out to have to play 4♠ in a 4-3 fit... well, that is character building. Although... if partner has a hand of normal opening strength or better (if not he will have to bid 2♠) he should be able to show he has only four spades over your Drury bid. For instance: 2NT now shows 4-3-3-3 and 12-14, 3NT 4-3-3-3 and 18-19 (assuming you play a 15-17 1NT opening). This is not very common though: many pairs play a 2NT reply to Drury as forcing.

There is one snag: Ed and I assume that you only open 1♠ on 4-3-3-3, since it is common in most countries on the European continent to open the lowest four card suit (if you open four card suits, that is).
However in original Acol (very common in Britain) it is quite common to open 1♠ on various hands with two four-card suits (usually in combination with a 12-14 1NT). As a consequence, 1♠ opening bids on a four-card suit are much more frequent.
A possible solution is the so-called Two-way Drury: you either respond 2♣ or 2♦.
2♣ (on your actual hand) shows exactly three-card support.
2♦ — so this is conventional too — shows four-card support or better.
Both responses show at least 10 points.
I strongly recommend you not to just start playing this without discussion, but first to work out a (simple) scheme of opener's rebids. Thus you prevent misunderstandings, which are very annoying for your opponents.

To conclude: Ed wrote I hid a diamond in my spade suit. Totally untrue, because that would be stupid, wouldn't it? I mean, the idea is to hide a card that will not catch the eye. So I hide a heart between the spades! A major suit card in a major suit, right? Sometimes Ed can be so dim...

En hils fra Orkanger