Roman Exclusion Blackwood

Normally one would not ask for aces when holding a void since it would not be possible to determine if an ace was in the same suit as the asker's void while another suit was unprotected.

Exclusion Blackwood solves this problem by jumping in the suit in which he is void after trump has been agreed (explicitly or implicitly via an artificial bid).

"Jumping to what level?" you may ask. Well.... 

One web site says it can be on the 4 level as long as it is a jump bid. 
Another says that it has to be on the 5 level. 
A third says that the bid must be above the level of game in the trump suit.

Responder shows his key cards by bidding up the line from the asking bid as he ordinarily would except that a key card in the suit bid by asker is not counted (so there are only 4 key cards).. 

The first 2 steps show either 1|4 or 0|3 key cards without the Queen of trump.. 
The 3rd step shows 2 keys WITHOUT the Queen.. 
The 4th step shows 2 keys WITH the Queen.

If responder couldn't show the Queen (because of having to bid one of the 1st two steps), asker can ask for the trump queen and side-suit kings (outside the exclusion suit) by making the cheapest bid (but not the trump suit) after responder's bid. 

Responses to the Queen-ask:  
Bid the trump suit without the trump Queen. 
Bid 5N with the trump Queen and no side-suit Kings outside the exclusion suit. 
Bid a non-trump suit with the trump Queen AND the King of the suit you are bidding. 

Example of Roman Exclusion Blackwood:

Responder's hand:  Axx QJTx Ax xxxx

1 - 3
4 - 4N = 1 key card
5 - 5N = trump Queen but no outside Kings.

Change the Hearts to JTxx and instead of 5N, the bid would be 4 = no trump Q.

Or change the Clubs to Kxxx and instead of 5N, the bid would be 6 = trump Q + K.