The only result more disappointing than being set in a slam is missing a cold one. So what do you do when you are faced with both possibilities?

In example hand 1, North had never heard of the prohibition against bidding Blackwood with a void. Partner's response, showing one ace, was accurate, but not the information North needed. "Which ace?" North wondered. If it's the A, there are two inescapable losers.

For bidders in this quandry, the salvation called "cue bidding" was invented.

North jumped the gun in another way, too. He didn't know the limit of opener's hand. A 1 opener could be as skinny as the hand shown, or contain most of the missing face cards, or anything in between.

Cue Bidding Rules

1. After a strong (game forcing) suit agreement, the bid of any other suit shows a slam control, not length.
2. The first time you bid a slam control, it shows first round control (the ace or a useful void).
3. The second time you bid a slam control, it shows second round control (a king, allowed only when the partnership owns all four first-round controls, trying for grand slam).
4. Don't ask for slam controls until after partner has limited his hand. In other words, don't go trying for a slam (either by cue bidding, Blackwooding, or Gerbering) until you know what level you belong at (33 to 35 points for a small slam, 36+ for a grand slam).
5. Avoid Blackwood (and yes, Gerber, too) when you hold either a void or a side suit with no controls (Aceless and Kingless). Cue bid instead.
6. When cue bidding, make things easy on partner by skipping over the controls you know about, bidding the control just below the one(s) you're missing.

In auction 1A, by settling for game and not cue bidding, South shows a minimum and limits his hand (13 to 15), but North presses on by cue bidding just below the control he is missing (5). South cooperates by denying both red aces (5). Armed with the information that partner's controls are not in hearts, North can now bid the small slam and be done with it.

Using Responder Count, North adds the value of his own hand (23-ish) to the average of his partner's announced minimum (14) and realizes that a small slam is very likely there somewhere.

In Example Hand 2, South envisions a slam comprised of a fully fledged trump suit and solid red cards. He realizes that if North is able to contribute the A and any club control (the ace, a void, or even a singleton) six is there for the taking.

South gets the cue bid ball rolling with his 4 call. Even though this seems to skip over the minor suits, it doesn't imply that he owns them. To the contrary, North should understand South's implied need: if he is cue bidding, he is missing something for a potential slam – something that a Blackwood question won't answer. Since North holds no first round controls at all, he has an easy denial, retreating to the home suit (4). Though disappointed, the pair avoids a slam and doesn't even go beyond game for having investigated the possibility.

These two examples show only two cue bidding situations. Slam bidding is a complex operation and cue bidding is only the beginning. An accomplished partnership will carry an arsenal of conventions and understandings which avoid unmakable slams and launch them into slams others miss. For further reading, try the following.

Bridge Bidding Made Easy. Edwin B. Kantar. Wilshire Book Company. 1978.
ISBN 0-87980-012-7.
Chapter 18, "Slam Bidding With Balanced Hands"
Chapter 19, "Slam Bidding With Unbalanced Hands"

Further reading on this topic:
Bridge Bidding Made Easy by Edwin B. Kantar