2NT Stopper-Ask

After a Weak 2-Bid, responder can query opener with 2NT for aces or kings in lower-ranking suits. With no sidesuit honors, opener can bid 3NT showing 2/3 top honours in the opening suit, or 3 in the opening suit with only 1. 

Usually this method is best after weak 2D since you often should play game in NT after 2Dopening. After 2H/2S you probably will end in the opening suit. So then it may be more important to ask for short suit.