The origin of this conventional method is unknown. The designation can be either two words or one word as in Jump Ball or Jumpball. The concept behind this conventional method is to employ it after an opponent has opened the auction with 1 No Trump.

The term jump ball is defined as a method of starting play or determining possession in which an official tosses the ball up between two opposing players who jump and try to tap the ball to a team mate.

Priorities

The range of the No Trump bid should be determined and/or announced before implementing Jump Ball since the values should be adjusted accordingly by the intervening bidder.The holding of the intervenor should be of a distributional pattern in order to justify an overcall.

The distribution can be a one-suited holding, a two suited holding, or natural. The following outline shows the general guidelines for the Jump Ball defense method. The reader should be aware that, as with all defense methods, there is a certain element of risk inherent if the values are considered minimum. The recommendation is that a consistent evaluation method be applied by the partnership before employment.

Jump Ball Guidelines

Double:	This call is artificial and alertable. When the partner of the No Trump bidder passes, then the advancer is required to bid 2, which is a so-called puppet bid. The intervenor, following a pass by the No Trump bidder, then clarifies his holding according to the following guidelines: Pass: Promises a one-suited holding in Clubs. 2: Shows a red two-suited holding: Diamonds and Hearts. 2: Shows a two-suited holding in both Major suits. 2: Promises a one-suited holding in Spades and otherwise additional values in side suits.
2 :	This bid is artificial and alertable. It is a multi-purpose bid and promises either a one-suited holding in Diamonds or a two-suited holding in Clubs and an unspecified Major suit. The advancer is required to bid 2. The following rebids by the intervenor clarifies his holding: Pass: The intervenor holds a one-suited holding in Diamonds. If passed out the advancer becomes the declarer. 2: This rebid by the intervenor shows a two-suited holding in Hearts and Clubs. 2: This rebid by the intervenor shows a two-suited holding in Spades and Clubs.
2 :	Promises a two-suited holding with Diamonds and Spades.
2 :	This overcall is natural and competitive. Promises at least a 6-card Heart suit or a 5-card Heart suit with at least 2.5 to 3 winning tricks. The overcall is non-forcing for the advancer.
2 :	This overcall is natural and competitive. Promises at least a 6-card Spade suit or a 5-card Spade suit with at least 2.5 to 3 winning tricks. The overcall is non-forcing for the advancer.
2 NT:	This overcall promises a holding containing both Minor suits. The advancer bids Clubs if Clubs is the preferred suit and Diamonds if Diamonds is the preferred suit.

If you wish to include this feature, or any other feature, of the game of bridge in your partnership agreement, then please make certain that the concept is understood by both partners. Be aware whether or not the feature is alertable or not and whether an announcement should or must be made. Check with the governing body and/or the bridge district and/or the bridge unit prior to the game to establish the guidelines applied. Please include the particular feature on your convention card in order that your opponents are also aware of this feature during the bidding process, since this information must be made known to them according to the Laws of Duplicate Contract Bridge. We do not always include the procedure regarding Alerts and/or Announcements, since these regulations are changed and revised during time by the governing body. It is our intention only to present the information as concisely and as accurately as possible.