When it appears from the bidding that you and your partner are very strong together, you think of examining a slam contract.
The course of the first bids determines the later method to be applied. We distinguish two bidding courses: Experience learns that in the first case usually the bidding ends up in a NT contract. Is very hard to exchange controls in NT bidding courses. For that reason in MAF, Gerber is enabled. From the table, which comes soon, you may conclude that this gives a lot more useful information than Blackwood would have done.
It is allowed to examine your hands first with Stayman or Jacoby, before applying Gerber. As long as you don't bid on the 4-level, Gerber counts always. When the bidding goes beyond that border Blackwood counts instead.

The bidding series of the second case appear often to end up in suit contracts. After establishing the trump suit (with strong hands), the exchange of controls is started, and subsequently Blackwood might be applied to ask for Aces and Kings.

The description of the typical agreements is given in the next diagram.

Meaning of RESPONSES to the "Number of Aces question"
The final contract will be in NT
trump suit has
been established
trump suit not
yet established
4 0 or 3 Aces 5 0 or 3 Aces 5 0 or 3 Aces
4© 1 or 4 Aces 5 1 or 4 Aces 5 1 or 4 Aces
4 2 Aces 5© 2 Aces 5© 2 Aces
4NT 2 Aces + 1 King 5 2 Aces + trump King and/or Queen 5 2 Aces + 1 King
5 2 Aces + 1 King + 5-card 5NT 2 Aces + void 5NT 2 Aces + 2 Kings
5 2 Aces + 2 Kings 6 2 Aces + trump King and/or Queen + void 6 2 Aces + 2 Kings + 5-card
5© 2 Aces + 3 Kings    
5 2 Aces + 3 Kings + 5-card
5NT 2 Aces + 3 Kings + 5-card
6 2 Aces + 4 Kings
6 2 Aces + 4 Kings + 5-card
The cheapest rebid by the 4 bidder after a response of 4 or 4©, is asking for Kings and beyond 4© it is asking for Queens If the rebid of the 4NT caller is in the trump suit or in NT, the bid is always final. All rebids in potential trump suits or in NT are always final bids.

It is clear that before asking for the number of Aces, you should commonly know, which suit is going to be the trump suit. In MAF there are many ways to establish the trump suit:

Sometimes it happens that during the control bidding one of the the players is convinced already, that small slam certainly can be made. This player should then consider seriously to call grand slam. To examine this possibility he could decide to skip the Blackwood 4NT bid, and do the 5NT grand slam convention instead.
This convention can only be applied to establish grand slams in suits. Next table shows how the 5NT convention works.

To examine a N.T. grand slam in a sound way, the modified Gerber convention should be used. Gerber was explained in the table before.

Meaning of the FORCED RESPONSES to a bid of 5 N.T.
after having established the trump suit and after having executed a chain of control bidding exchanges
and: without calling 4NT before, or by the 4NT caller after hearing 2 or more Aces; never show trump Ace twice
to 5NT

intended TRUMP SUIT
6 sign off no A/K no A/K no A/K
6 - A/K A/K no A/H but L/Q
6© - - A/K + L A/K
6 - - - A/K+L
7 A/K+K/Q A/K+K/Q A/K+K/Q A/K+K/Q
Explanation symbols:       A/K = Ace or King ,  L/Q = Length or Queen   in the trump suit.          = any trump suit

It is not necessary to jump to 5NT to make this bid conventional. If the exchanging of controls went on beyond the 4NT level, the only fly way left is a 5 - or 6-level bid in the established trump suit. When 4NT has been called, commonly the the conventional meaning of 5NT doesn't count any more, unless 2 or more aces have been shown, but in that case an eventual aces in trumps cannot be declared a second time after the 5NT. In other cases 5NT is a final bid.

The diagram shows that the response never exceeds the 6 level. The nearer the response approaches it, the stronger is the support. With the strongest support imaginable, the responder should always call the grand slam.

When you want to see bridge games, in which the principles, described above, are applied, you should click for examples, and make your choice when you're arrived there.