Gerber is a contract bridge

Contract bridge

Contract bridge, usually known simply as bridge, is a trick-taking card game using a standard deck of 52 playing cards played by four players in two competing partnerships with partners sitting opposite each other around a small table...

 convention

Bridge convention

A bridge convention is a system of calls made during the auction phase of a contract bridge game which conveys a coded meaning about the players' card holdings...

 devised by Dr. William Konigsberger and Win Nye from Switzerland who published it in 1936; John Gerber of Texas introduced it to North America in 1938 where it was named after him . It is similar to Blackwood

Blackwood convention

In the partnership card game contract bridge, the Blackwood convention is a popular bidding convention that was developed by Easley Blackwood. It is used to explore the partnership's possession of aces, kings and in some variants, the queen of trumps, to judge more precisely whether slam is likely...

 but uses 4 instead of 4NT as an "asking bid" to inquire about the number of aces held by partner; a further asking bid may follow to inquire about the number of kings held.

Gerber is used primarily after notrump openings, responses and rebids, making it a complement to Blackwood rather than a replacement.

Purpose

Because bidding and making a slam

SLAM

Slam or SLAM may refer to:In computer science:* Simultaneous localization and mapping, a technique used by robots and autonomous vehicles* SLAM project, a Microsoft Research project...

 or grand slam

Grand Slam

Grand Slam may refer to:-Card games:* In the game of contract bridge a bid to win all the tricks of that hand. By extension, the taking of all the important elements in an endeavour.-Equestrianism:...

 contract in bridge gains significant bonus scoring points, partnerships will strive to bid them whenever their combined card assets are deemed sufficient. Knowing the number of aces and kings jointly held is usually crucial to this decision and Gerber is one of several bridge conventions used to ascertain the necessary information.

Responses and continuations

The ace-asking bid is 4. The criteria for its application varies amongst users and alternatives are detailed below; likewise, a number of response schemes have been developed over the years. Partnership agreement is required on both matters.

Original response scheme

The original responses to the 4 asking bid are:

• 4 = 0 aces
• 4 = 1 ace
• 4 = 2 aces
• 4NT = 3 aces
• 5 = 4 aces

Modern response schemes

Most modern bridge literature recommend the following response scheme:

• 4 = 0 or 4 aces
• 4 = 1 ace
• 4 = 2 ace
• 4NT = 3 aces

However, some experts favor the following responses, analogous to Roman Key Card Blackwood:

• 4 = 0 or 3 aces
• 4 = 1 or 4 aces
• 4 = 2 aces

Other response structures have been devised along similar lines and partnership agreement is required to establish a preferred scheme.

Continuations

Like Blackwood, a follow-on bid may be used in Gerber to ask for kings. There are two principle approaches for the king-ask bid:

• Bid 5 to ask for kings or
• Use the next available bid, skipping the trump suit if one has been agreed, to ask for kings.

Step-responses mirror those for the ace-ask bid.

Comparison with Blackwood

The main perceived advantage of Gerber is that it is bid at a lower level and therefore allows for a final contract lower than does Blackwood (in the event that insufficient aces are present). This lower level also allows for an exploration of kings in more cases. A second advantage is that it is highly suitable for potential notrump contracts, whereas with Blackwood a final contract of 5NT may be confused with a bid asking for kings. For this reason, many use Gerber when the potential contract is in notrump.

Partnership agreement

Depending on the auction context, a bid of 4 may have several meanings; it might, for example, be confused with a splinter bid

Splinter bid

In contract bridge, a splinter bid is a convention whereby a jump bid in a side-suit indicates a trump fit and a singleton or void in the suit bid. For example, a 4 clubs response to a 1 heart opening establishes hearts as trump suit and indicates a singleton or void in clubs. Most experts agree...

 or a cue bid

Cue bid

In contract bridge, a cue bid is a term that applies to two types of bid:*A bid of a suit that has already been bid by opponents.*A slam-investigating bid made during an auction's later rounds that shows control of a suit...

. For this reason, it is important that partnerships agree, in advance, when 4 is Gerber.

Possible partnership agreements for distinguishing 4 as Gerber from other meanings of 4 are:

• 4 is always Gerber.
• 4 is Gerber only if the immediate preceding bid by partner was in notrump.
• 4 is Gerber unless a natural club suit bid has been made by the partnership.
• 4 is only Gerber when in response to opening bids of 1NT, 2NT or a strong artificial 2.
• 4 is Gerber if it is a jump bid or if a suit has been agreed as trump.

In addition, agreement is required on how to handle responder holding a void and on opposition inteference in the bidding.