Openers responses to 2
Responders rebids
If responder's first bid was 2 the only bid he can pass is 2NT. Some play that
responder can show a real bust over any suit bid by opener by making the cheapest
3 level bid.
Interference
If your partner opens 2
and your RHO bids then a pass by you
promises a king or an ace and a double denies a king or ace.
If your RHO doubles then a redouble by you denies a king or ace
and a pass shows a king or an ace.