Convention Basic

Basically all of the convention to ask for the Ace is in the hands of a partner can be said is a variant of Blackwood convention, as well as the Gerber convention, only if Blackwood using bidding 4NT to ask Ace, while John Gerber uses 4C, convention on the bridge aimed to determine the number of Ace in the hands of a partner towards the game slam or grand slam, but if it does not meet the expected needs Ace then the player will generally play in the game only.

Example : A bid to the game alone convention
1. Opener        Responder
     2S               3S
     4C              4H
     4S               pass
Opening 2S for this system indicate point 16-20, and the spade have a minimum of 5 pieces, then opener rebid by 4C, 4C are called the Gerber convention,

The answer from Gerber 4C Convention is
4D shows 0 or 4 Ace
4H shows an Ace
4S shows 2 Aces
4NT shows 3 Ace

       From the example above shows that the responder answer with the 4H means having only one Ace, but the possibility opener takes two to play slam Ace, Ace is expected because of the need not comply then the opener will stop call on 4S.

Examples of cards that requires a handle Opener 2S 2 Ace to play slam invite, because responder supports color spades with a minimum of 3 pieces of honor in spades with a confirmed response 3S win all the tricks, then the opener dare to take the path that led to the convention slam.
Possible grip opener card is
S AKQ975                  or                     AKJ10954
H KQ6                                                KQ2
D 4                                                      K8
C KQJ                                                 K3

Handle the possibility of responder card is
S J32                           or                     Q86
H A1054                                             J10543
D KQ9                                                AQ3
C 975                                                  102

But when the handle with 2 Ace Responder then opener is likely to be brave to play Slam
Example: convention bid to slam
2. Opener                    Responder
     2S                           3S
     4C                          4S
     6S                           pass
When responder holds 2 Aces by answering the 4S, the opener will pull the trigger slam 6S

Handle the possibility of responder card
S J32                           or                     Q86
H A1054                                             J10543
D AQ9                                                A73
C 975                                                  A2

After knowing the number of Ace, the convention may be continued by asking the King if needed, and offer a step following the bidding responder

Example: Advanced conventions passed by asking King

3. Opener                    Responder
     2S                           3S
     4C                          4H
     4NT                        ?  responder answers also follows the step
                                      5C shows 0 or 4 King
                                      5D shows a King
                                      5H shows 2 King
                                      5S shows 3 King
      ?                              pass
From the example above if the opener rebid 4S, stop call, so opener rebid 4 NT to ask the King.
After the Responder replied by pointing out the general opener King will direct the final bid decision whether slam or grand slam.