After establishing a suit that will most probably be trump, more often than not the King of trumps will be as important as any of the Aces. For Keycard Blackwood, assume that King to be an Ace. (Five aces in this deck!? Well, let's call them "Keycards".) Even the Queen of trumps gets special treatment.     

     Two variants of Keycard Blackwood are often called 1430 and 3014. Here are the responses after an asking 4NT:

1430 Keycard Blackwood Responses :

5 shows: 1 or 4 Keycards 5 shows: 3 or 0 Keycards 5 shows: 2 Keycards without Queen of Trumps 5 shows: 2 Keycards with Queen of Trumps 5NT shows: 2 Keycards with a Useful Void 6 // shows: 1/3 Keycards with a Useful Void

    Say "Fourteen Thirty" out loud. Write this on your convention card: 1/4 : 3/0 . You've agreed to play 1430 (Fourteen Thirty)
If you bid the first step after 4N, which is 5, you show one or four keycards (1/4): Fourteen.     
If you bid the second step after 4N, 5, you show three or zero keycards (3/0)" Thirty.

If you bid the next step, 5, you're showing two keycards.
Bidding 5 also shows two keycards.
The difference?: 5 DENIES the trump Queen while 5 SHOWS the trump Queen.

Test yourself: After partner asks for keycards with 4N:
How do you show one or four keycards? 5
How do you show zero or three keycards? 5
How do you show two keycards without the Trump Queen? 5
How do you show two keycards with the Trump Queen? 5

What would 5 show? Two WITHOUT the Trump Q, the third step above 4N.
What would 5 show? 3/0, the second step above 4N.
What would 5 show? Two WITH the Trump Q, the fourth step above 4N.
What would 5 show? 1/4, the first step above 4N.

In the auction:

1 Pass 3 Pass 4NT Pass ?

Spades has been agreed to be trumps.
Keycards in spades include A,K,A,A and A.
The Q IS NOT a keycard, but you might be able to show it.

Hand 1:	Axxx	Kxx	KJx	QJx	would respond 5, 1/4 keycards
Hand 2:	AQxx	Kxx	KJx	Jxx	would respond 5, 1/4 keycards
Hand 3:	Qxxx	Kx	Kxx	KQJx	would respond 5, 3/0 keycards
Hand 4:	KQxx	Axx	Axx	xxx	would respond 5, 3/0 keycards
Hand 5:	Kxxx	AQTx	xx	Kxx	would respond 5, 2 keycards Without the trump Q
Hand 6:	KQxxx	Axxx	xx	Kx	would respond 5, 2 keycards WITH the trump Q

In Hands 2, 3, and 4 , the responder holds the Q of trumps, but can't show it unless partner asks for it specifically by bidding the suit above the keycard showing response (if that suit is not trumps!).

     With Hand 5, the auction might proceed:

1 Pass 3 Pass 4NT Pass 5 Pass 5 Pass 6 Pass Pass Pass

4NT asks for keycards in spades
5 promised 3 or 0
5 asked for the Q
6 promised the Q and denied any other Kings.

     Choosing to show a useful void, by bidding 5NT or 6 of the void suit, entails some danger.
Often the void is not useful and keycards are lacking for success at the higher level.
Good partnerships can distinguish between whether 1 or 4 keycards are held, but some cater to the uncertainty by having the 4NT bidder bid 5 of the agreed suit if 0/1 keycards aren't sufficient for slam.
     Responders with 3/4 keycards then continue (in contrast to regular Blackwood when the 4NT bidder sets the contract.)

     Some agree that a jump to 4, after a NT rebid, is Keycard Gerber with likewise step responses.

     After a NT opening and jump to 4, there is no suit to use for keycard, but often Club honours are important, so assuming clubs trump for keycarding is not unheard of.

     Often 1430 is pronounced "fourteen thirty" for brevity. A no lesser alternative is to play "thirty fourteen" in which case the meanings of 5 and 5 are reversed.