Overcalling in fourth position doesn't obey the same rules as overcalling right after the opener...
Be careful ! Your partner has already passed, and may have a pathetic hand ! Pay attention to the vulnerability . Green vs Red, you shouldn't have less than: K108xx,KJ9xx,xx,x in the named suits.But, there is no upper limit !
Moreover, biddings have various significations. The meaning depends on the
number of suits the opponents have named (1 or 2). Have different meanings :
- cue-bid of the opener's suit
- 2NT overcall
NT is calling for the two weakest suits. The opponents have named only one suit !