In Parts I and II you were introduced to the golden rules of cuebids, and the basic principles of the sweep cue-bid system. Recapping briefly:
Sweep cues are not fully compatible with the "Italian style" of cuebidding, where the first cuebid in any suit can be either the ace or the king, and bypassing a suit implies you hold neither the ace nor the king. The basic problem is that if partner cuebids a suit where you hold xx or xxx, you still don't know if that suit is controlled adequately to bid a slam.
You can, however, squeeze some extra mileage out of cuebidding auctions by allowing kings to be shown in situations where your partner will almost surely find your king to be a useful card. Here is the rule Michael and I used, adopted almost verbatim from Brashler: in a suit bid naturally by your partner, you may freely cuebid either an ace, a king or a void the first time you cuebid the suit.
Notice that you may not show the king of your own suit before the ace, unless partner has raised you. Partner may well be short in your suit!
Normally the first cuebid of a suit shows the ace or a void; the second cuebid of a suit (either you or your partner has already shown first round control, or you have previously denied first round control) shows the king or a singleton; the third cuebid shows the queen or a doubleton. The corollary to treating the ace and king of partner's bid suits as equals is that the second (positive) cuebid in the suit also shows either the ace or the king (or a singleton or void).
One potential partnership misunderstanding: suppose you have previously denied possession of either the ace or the king of partner's side suit. if you cuebid this suit at your second opportunity, are you showing a singleton? Or are you showing the queen? (My field experience is that this shows a singleton, and I will treat it that way in this article. Brashler's book implies it shows a queen.)
"Well," you ask, "what if opener wishes to explore further for slam anyway?" There are still a couple of options. One, if partner has extremely good trumps, he can continue over your 4 bid if he thinks slam is still in reach. Two, there may be negative inferences from the fact that partner was unable to sweep to the five-level himself. Three, if your hand is so good that the only thing you are worried about is trump quality -- say you have all three side-suit kings in your own hand, for instance, don't forget about two conventions of good old-fashioned standard... the voluntary raise to 5 of a major, and the Grand Slam Force.
To formalize the notion of "good trumps," we suggest that the ace, the king, or the Q-J is enough to how good trumps once (these holdings are good enough to normally guarantee no more than 2 trump losers if partner has only small trumps, and no more than 1 trump loser if partner has one high honour.) Showing good trumps twice promises two of the top three.
Playing Sweep Cues, you will be using the Grand Slam Force in a lot more often than you were accustomed to in your simple cuebids and Blackwood days. Playing RKC, you use the space between 5M and 6M to find out about the queen of trumps and side-suit kings; playing Sweep cues you'll already know about side-suit kings by the time you reach 5M and trump quality will often be the only thing left to ask about.
You won't be surprised to hear that we have formalized the responses a bit more than the old-fashioned "bid six with zero or one top honour, bid seven with two." The answers vary according to whether you have previously promised good trumps in the cuebidding auction or not, and according to what suit is trump, but as logically as they can. Here is the basic structure if hearts are trump:
Similar sets of responses can be constructed by common sense and partnership agreement for other situations: if you've already promised two of the top three trumps, for instance, GSF asks you how good: 6 KQ; 6, AQ; 6, AK; higher, all three. If you've already denied possession of good trump: 6, small cards; 6, J; 6, Q.
As in "standard" GSF, if spades are trump you have an extra step (I use it for 6 = A or K without the jack, 6 = AJ or KJ), if diamonds are trump you don't have room to distinguish which honour partner has, and if clubs are trump it becomes a simple yes/no question.
You and your partner can agree on whatever schedule of steps you find easiest to remember. I do, however, strongly recommend that you adopt the "6NT = all my cuebids were high cards, 7M = at least one of my cuebids was shortness" agreement -- it is invaluable for making good decisions about that extra 10 points for bidding 7NT in matchpoint games.
In Part IV, we look at several real-life hands and see how Sweep Cues handle them.