Bridge & other card games/Roman Key Card
Using RKC 1430 who do I know what my partner means by responding 5 clubs to a 4NT bid?
Playing 1430 a response of 5C over 4NT shows either 1 key card or else 4 keycards. It will usually be obvious from the auction and from your hand whether partner actually has one or 4. However, in the rare case you are unsure and partner having one keycard is not enough for you to bid a slam, then just sign off in five of the trump suit. If partner has one keycard he will pass but if he actually has four keycards then he should reveal the good news to you by bidding a slam over your sign off. Thus, the 5C response is the "14" part of 1430.
If partner instead 5D, he would show 3 keycards or else 0 keycards. That is the "30" part of 1430. Again, most of the time it should be clear from your hand and from the auction which one of these partner actually has.