The concept behind any jump shift in the Romex Bidding System is that the bid is forcing. The idea is similar to the Two-Over-One bidding system, which guarantees game. After an opening bid, if the responder bids and then rebids any other suit except the first named suit, then a game-forcing situation has been created. The strong jump shift by the responder promises at least 16 plus points and a semi-solid or solid 6-card plus suit.
The length of the suit can be downgraded to a 5-card suit if there is an established fit with the opener. The jump shift also promises five plus controls and less than five losers. The feature of the jump shift also strongly indicated that the responder held no other 4-card side suit, unless it was possibly the suit of the opener.
This definition for the jump shift is rather restricted to holdings, which do not occur that often and are rarely applicable. However, this particular definition gives the partnership a certain advantage of immediate clarification when such a holding does occur.
The rebids by the opener are also clearly defined and are narrowed in definition, in order to describe, as best as possible, the holding. These rebids are described and listed below:
A. If the opener holds an honor in the jump shift suit of the responder, even if it is a singleton, then the opener is required to raise the suit of the responder. The opener may do so in two different manners:
In the case that the opener raises the suit of the responder, the assumption is that the suit of the responder is a solid suit or at least a semi-solid, sound suit. The responder then can raise the suit of the opener, the established trump suit, and this raise then becomes Keycard Blackwood.
The responder can also rebid:
B. If the opener holds no honor in the jump shift suit of the responder, the opener has several options to describe his holding:
C. The responder then has several options:
D. The opener then has several options:
The responder, in providing additional information, may cuebid by rebidding a new suit, which establishes the original suit of the opener as the trump suit. The responder also has the option of bidding 4NT, as a slam attempt, which is Keycard Blackwood. This confirms the assumption that the original suit of the opener is the established trump suit. However, a rebid by the responder of his suit establishes this suit as the trump suit.