This designation is otherwise known as Informative Discard From a Sequence. The origin of this discarding method is unknown, although there is a strong argument that the method has been adopted from developments practiced in the early days of the game of Whist and integrated into the game of bridge at an early stage of the evolution of duplicate bridge.
Foundation of the Concept
The sequence discarding method is only employed by the defending side. The reasoning behind sequence discards lies in the fact that a held sequence consists of a row of touching cards (normally honor cards), which will produce a winning trick. A sequence is generally defined as two or more cards in consecutive order of rank, such as AK, which is a sequence of two cards, or QJ10, which is a sequence of three cards, or J1098, which is a sequence of four cards. Each of these sequences may produce a trick when defending.
Normally, when the lead is from a sequence such as QJ10 the player denies the possession of any higher honor such as the Ace or King of that suit.
This reasoning also holds true when the player is forced to discard. By discarding, for example, from the three-card sequence QJ10, then discarding the Queen denies the possession of any higher honor such as the Ace or King of that suit. This discarding method has become designated as sequence discards. It is a discard communicating that the player does not have any higher ranking card in the discarded suit, but informs the partner that the J10 is held.
Note: This sequence discarding method is only applicable if the discard is logical and applicable to the play technique of the declarer.
Note: The same principle applies in following suit after a top honor card has already been played in that particular suit. This follows the more general principle of discarding the highest card which can be spared in transmitting an informative signal to partner.
Note: The method of sequence discards do not transmit any information about attitude, or count, or suit preference. The method only informs partner of the holding of a sequence and the denial of any higher-ranking card or honor.
Example
In the following example the declarer is South. The contract is 4 Spades. West leads the Ace of Hearts, East plays the Jack of Hearts. On the second trick West follows with the King of Hearts, and East discards the Queen of Diamonds, which promises a sequence in Diamonds. This action, in turn, promises at least one winning trick in Diamonds in case the declarer holds three Diamonds.
A logical conclusion can be made that the discard of the Queen of Diamonds affords the partnership the opportunity to communicate the information that a sequence is held as opposed to no agreement, whereby East can indeed discard a Diamond, which carries no information.
In the case that there is no partnership agreement, then the player may discard any one card of the sequence since each card carrys the same value in play, meaning that the Queen of Diamonds holds the same values as does the 8 of Diamonds in this particular suit sequence.
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 tThe o 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.