Grand Slam Force - let's talk royalty
When you are almost sure that a Grand Slam is there, the suit is agreed, and all you need to know is something about the trump honours, then you bid 5NT, known as a "Grand Slam Force".
Partner replies 6 of the agreed suit with only one of the top honours, but bids 7 with two of them.
You can't use this technique after starting Blackwood 4NT, as the bid will be confused with the question "How many Kings do you have ?".