When you are in a trump suit the K of trump is nearly as important as any ace. Also the Q of trump is a very important card. Therefore, the Blackwood convention was enhanced to allow asker to find out about the K and Q of trump. The enhanced system is called Roman Key Card Blackwood (RKCB). Here, the trump King of trump and the 4 Aces are counted as “Key Cards”. So now, instead of having up to 4 aces to show, you know have up to 5 “key cards” to show.