Source: Ginny & Jeff Schuett for 
Cuebidding without interference is an attempt to get to slam without using Blackwood, or before using Blackwood. Usually the cuebid takes place between the three and four level in our agreed major or higher. It can also be used whenever both members of the partnership know we are going to game, and new suits are introduced.
A common example of this is when we open 2
and responder bids a game forcing 2
. Sometimes the cuebid is made after we explicitly raise one another, and sometimes it is made to show a strong raise of the last naturally bid suit.
The common American cuebid style is to cuebid first round controls (ace or void) first. Cuebid second round controls (king or singleton) only after the first round has been shown. Cuebids are especially valuable as a slam invite after splinters or Jacoby 2NT is bid, and the hands appear to fit well. They are often used when you want to use Blackwood, but have a weak two-loser side suit, and you want to find a control there before launching into Blackwood. Look at the following:
South’s jump to 3
is strong and with North’s HCPs, slam seems likely, but there is a risk. North doesn’t have a club control and North have two fast club losers. Cue bids identify the needed controls and RKC (Roman Key Card) leads to bidding the 6
slam.
North’s 3
is natural and forcing. South bids 4
to show a strong raise to 4
with the
A. North used RKC, and when South showed three keycards, he bid 5NT to show all the keycards and asks for kings. NS play to show specific kings, so 5
showed the
K and denied lower ranked kings, so se led for 6
. With careful play, North can set up diamonds as discards, and could make all 13 tricks.
Cuebids are usually the best way to start thinking about slam and soliciting control information from partner. This is especially true if one hand holds a void and specific controls are key to bidding a good slam or even grand slam. Most players are too anxious to jump to 4NT rather than bid slowly to get the key information through cuebids first. Blackwood can always be used after the cuebid, and remember, all responses to Blackwood include all controls already shown via cuebids. Good luck.
