Bridge bidding -- the jump-reverse rebid by opener.

Jump Reverse Rebids by Opener

This convention solves the opening bidder's problem of how to accurately describe a minimum 6-5 hand that has greater length in the lower-ranking suit. For example, if you're opener with 4 KQJ93 AJ10765 4 you have a dilemma. If you open 1H, the best you can do is show 5-5 distribution by rebidding diamonds twice. If you instead open 1D, you can show your 6-5 pattern by rebidding 2H and 3H, but that creates a reverse auction that shows significantly more high-card strength.

The solution is to use the jump in the higher-ranking suit as natural, limited and non-forcing. With the hand above, you open 1D. Over partner's 1-level suit or notrump response, you rebid 3H to show a 6-5 hand with minimum high-card strength.

Opener's Rebids

The requirements for using a jump-reverse are:
1-You're the opening bidder and have 6-5 distribution, with 6 cards in the lower-ranking suit.
2-You have the playing strength (but not the high-card values) to play at the 3-level opposite a minimum response. This means your suits should be strong -- ideally, most (or all) of your honor cards will be in your long suits. For example, a jump-reverse is not recommended with a hand like

K A J6542 KJ10643. With this, just open 1C and rebid 2C.
3-You have minimum high-card values (10-15 pts.) -- a hand that's worth an opening bid, but has less than full reversing values (16-17 pts.).
4-Responder makes a 1-level bid that bypasses your 5-card suit -- i.e. you must go to the 2-level to bid your second suit. (You may also use the jump-reverse if an opponent's overcall has forced you to the 2-level, whether or not partner has responded.)

Jump-Reverse Auctions

Typical jump-reverse auctions that carry this meaning include:
1C-1H-3D 1H-1NT-3S 1D-1S-3H 1C-(1H)-1S-(P)-3D 1C-(P)-P-(1S)-3H

Note that you do not use the jump if partner's response leaves you room to show your second suit at the 1-level. If you open 1D with AK874 Void QJ10863 K4 and partner responds 1H, a jump to 2S should be a strong jump shift (19+ pts.). With the hand above, you can show your pattern and minimum values by simply rebidding 1S and then 2S.

Note also that you do not promise 6-5 distribution if you jump after partner has made a negative double. After the auction 1C by you -- (1S overcall) -- Double by partner, your jump to 3D or 3H would be a simple value bid, promising at least 4-card support and invitational strength.

Most pairs who play this convention choose not to apply it if partner makes a 2/1 response, especially in a 2/1 forcing-to-game system. After 1D by you -- 2C by partner, it's best to rebid only 2H with A QJ976 A109864 4. This saves space and allows you to use a jump to 3H here as a splinter (good club support, singleton heart, big hand).

Responder's Rebids

Opener's jump-reverse is not forcing. Responder can pass or take a signoff preference back to opener's first suit if he has no interest in game. In general, it's assumed that opener has given a complete description of his hand, so it's up to responder to place the contract.

Responder should evaluate his holdings in opener's suits and stretch to bid game if he has fitting cards. Based on the Losing Trick Count, opener will usually have a hand with 4 (possibly 5) losers. Responder should bid a major-suit game if he has a fit and can cover 1.5-2 of opener's losers. He should bid a minor-suit game if he has a fit and can cover 2.5-3 of opener's losers.

After the auction     Opener         Responder
                                  1C                1S
                                  3H                 ?
the meanings of responder's rebids are:

     1-Pass = a weak, possibly non-fitting hand that prefers opener's second suit -- KQ1032 763 KJ8 54. Partner will most often be 1-1 in the outside suits, so you can't count your kings as covering any of his losers.
     2-Preference to opener's first suit (4C) = a weak, possibly non-fitting hand that prefers opener's 6-card suit. This is a signoff, and opener should pass.
     3-Game bid in either of opener's suits (4H or 5C) = to play. Opener should always pass. In the auction above, if you hold A9854 1043 432 K9 , you have at least two of partner's losers covered (a club and a spade, plus a possible club ruff), so you should bid 4H. Similarly, with A9854 10 9432 K97 , you have at least 3 losers covered (a spade, a club and 1-2 heart ruffs), so bid 5C.
     4-Rebid of your suit (3S or 4S) = to play, showing great length in your suit and probably no fit for opener's suits.
     5-3NT = to play.
     6-4NT = key-card Blackwood for opener's second suit.
     7-Fourth suit (4D) = a slam-try in opener's first suit. Opener should cuebid a below-game first-round control (4H or 4S) if he has one, or he can use key-card Blackwood if he wants to immediately accept the slam try. Any subsequent Blackwood bid by opener or responder is key-card for opener's first suit.
     Alternatively, if opener has a first-round control in the fourth suit and a cuebid of that suit would be past game (as 5D would be in the auction above), you can agree to use opener's 4NT rebid as a cuebid of the fourth suit. After 1C-1S-3H-4D, opener's 4NT would show an ace or void in diamonds, but no first-round control of hearts or spades.
     Yet another variation is to use responder's fourth-suit bid as key-card Blackwood for opener's second suit. Partnerships should discuss these auctions and decide which treatment they prefer.
      8-Below-game raise of opener's second suit (1C-1S-3D-4D) = invitational to game, showing a fit and a hand that can cover 2 losers.

Summary

This convention can be a very valuable addition to almost any Standard American-based system. It's especially effective in finding short-point games and slams, and can have preemptive value. Using the jump-reverse as non-forcing does not require you to give up any other meanings, as the jump is an otherwise idle bid. If opener has a very strong high-card hand, there's no need to jump -- he can still show his 6-5 distribution by making a forcing 2-level reverse and then rebidding his second suit.

The main disadvantage is that although the jump rebid gives a close-to-perfect description of opener's hand, it takes the auction very high, very fast. If responder has a weak, non-fitting hand with shortness in opener's second suit, the auction will be propelled to the 4-level when he's forced to take a preference back to the first suit. To make best use of this convention (and avoid disasters), opener and responder must have advanced hand-evaluation skills and exercise good judgment.