INTERVENTIONS AGAINST THEIR 1NT OPENING   Suppose you have Jx AKJ10xx Q84 Jx and opponents opening is 1nt. Of couse you have no problem in overcall in 2 to disbub Opponent in find their best contract and also shows to partner where are your honors. But suppose now you have two suits: KQ973 KJ10xx Q8 x and you want to overcall. Many years ago the player with this hand overcall in 2 thinking that if they double then he could bid 2. Responder having a weak hand could not double because he was afraid that opponents find another suit so he pass. Advancer with singleton in partner's suit thought in bid 2 but was afraid in found partner with singleton Spades, so he also pass and the final contract became 2. The cards distribution was: Opener      Overcall      Responder  Advancer  J6           KQ972       5               A10843  Q94        KJ1032     A876         5  AK94      Q8             J107         6532  KQ10x    x               Jxxxz         Axx As we can see 2 may down 1 but playing in Spades it is possible to make 10 tricks! Finally, suppose you have Jx AJ10x KQ84 A8x and opponents opens 1nt. Should you double to find a fit in the reds? Of course not, your partner probably will bid a black suit and it is possible that your partner play 2 in the fit 4-2. Thus, against nt we should only double when we have 7+ sure tricks in our hand to punish opponent, like:  x Ax KQJ10984 A8x   or  AKQJx Ax A98 98x Conclusion: to overcall against nt opening we need a convention that may show situations of only one suit, situations of 2 suits and situations for a penalty double. Our recommendation it is that you and your partner should study 3+ good popular conventions, like: 1) meckwell <= used by Jeff Mechstroth and Eric Rodwell 2) D.O.N.T <= recommended by Bergen-Cohen 3) multi-landy <= an improvement in Cappelletti/Hamilton and then adopt it for you system.