Source: Slam-oriented auctions: Gadgets and GizmosMajor-suit jumps to the five-level
This subject was first covered in detail by Alan Hiron in Bridge Magazine 40 years ago, and I have never seen any reason to move on from the advice he gave. Alan split the five-level jumps into three separate categories,
(1) Trumps
(2) Danger-suit
(3) Unbiddable extras
Barry Rigal
The default meaning for a jump to the five-level (which has become somewhat less important with the advent of Keycard Blackwood) was always to focus on trumps, suggesting slam values but significantly worse trumps than partner might have expected.
An auction such as 1-1-3-5suggests four small trumps but the values for slam. Even jack-fourth would probably be too good for this sequence these days, since KQxx opposite is a perfectly acceptable trump suit and one could identify that holding via Keycard Blackwood.
An extension of this idea is to go to the opposite extreme – this may sound dangerous but there should never be any confusion (trust me I’m a doctor). The five-level call can also be used to show extremely good trumps with nothing to cuebid.
The 4call is a cuebid for spades, and the final call by responder might be based on a hand like:A-K-Q-J-x-x x- x-x x-x-x. Slam might be excellent facing e.g.
10-x A-K-x-x A-K-x-x-x A-x or undesirable facing x-x Q-J-x-x A-K-Q-x-x A-K.
Typically a weak hand facing a strong hand can use this call to get all the values across at one go. An action like 2-2-3-3-4-5focuses on responder’s good trumps with nothing else to cuebid. Since Responder could have shown solid spades at an earlier turn by a jump to 3at the first turn or a jump to 4at the second turn, this should be semi-solid trumps and nothing else – maybe AQJ10xxx and out.
The second possibility for the five-level jump is to use the call to flag a danger suit. The suit in question will always be the fourth suit in an auction where the partnership has cuebid two of the three non-trump suits, or one where the opponents have overcalled or doubled a suit and the partnership has not subsequently shown a high-card control in that suit.
Reverting to an earlier auction, with a subtle change:
The 5call here suggests say A-K-J-x-x-x-x K-x x-x x-x. After the 4call responder knows his partner might have a hand with a club control and a minimum, or no club control. So Blackwood will not get the job done if you find an ace is missing.
Responses to this ask should see opener passing with no club control, raising to six with a minimum hand and the club ace or a singleton club, and cuebidding a new suit with first round club control and grand slam interest in context maybe:
Q A-x-x-x A-K-J-x- A-x-x. With a guarded club king, opener bids 5NT and lets responder pick a slam.
Equally on an auction such asresponder might have K-x-x x- A-x- A-K-Q-x-x. Here opener’s heart holding might make any number of tricks between 11 and 13 appropriate.
The third category of five-level raises or jumps tends to come in competitive auctions where one hand cannot get their extras off their chest.
sounds quantitative to me, not focusing on spades. Responder might have
x-x K-Q-J-x-x- A-x Q-x-x and feel that he is far too good to settle for game. But since opener was under the gun, he might easily have decent diamonds and a single spade stopper with only moderate extras. Particularly when all the suits have been cuebid, one hand might want to find out about partner’s range not just their controls.Suggests responder has a decent hand (Q-x A-J-x-xA K-x-x-x-x) but may just want partner to bid on with some extras, rather than focusing on the aces and kings.
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The 4
call is a cuebid for spades, and the final call by responder might be based on a hand like:
A-K-Q-J-x-x 
The 5
responder might have 
sounds quantitative to me, not focusing on spades. Responder might have
Suggests responder has a decent hand (
