Is it Exclusion, a Splinter, or Something Else?

One of the main issues a lot of people have with Exclusion Blackwood that they are afraid they will not recognize it when partner bids it. I suppose this is a legitimate concern unless you take some time to think about it. As a general rule, Exclusion Key Card Blackwood applies when you jump to one above a splinter. If 4D would be a splinter, then 5D is exclusion. If 3S would be a splinter, then 4S is exclusion. Since I started using it a few years ago, it has come up a lot more frequently that I expected. Twice this week, in fact, my partners had a chance to use it but didn't, and once last night, I could have used it but opted for just a jump to slam.

Holding AKx, void, KT9, AKQJxxx, you open 2C, partner says 2D, artificial and game forcing, you bid 3C and partner bids 3D natural. 4H would be a splinter, right? So 5H would be exclusion. Chances are slim that partner has AQxxxx of diamonds but if so, you want to be in 7 and should feel good about 6D anyway. Suppose partner responds 5NT showing 1 key card, then you can bid 6C to ask about the Q of trumps. Partner signs off in 6D without the Q, making 6 when he finesses the wrong way for the missing Q. It's not 100% clear that that is what those bids would/should mean, but that's how I see it.

On this other one, you hold something like: AKx, void, Qxxx, AKQxxx. This was with Sean, playing canape: he opened a Polish 1C, I bid 1H (8+ unbalanced, 4+ H), he bid 1S (17+ hcp, 3+S, not 4H), I bid 2D (longer diamonds than hearts). 3D here is surely natural and forcing, 4D is Key Card for diamonds, 2H is 3 card support, 5D ought to be a signoff, so 3H should be a splinter, and therefore 4H exclusion. Sounds reasonable to me. This would have been a nice grand on 28 hcp but it was just at a partnership bidding table anyway.

A standard auction surely would have started 1C-1D. Now what? How does one make a forcing diamond raise? You could fake a jump shift by bidding 2S and then support diamonds later. Since 2H is a strong jump shift, 3H must be a splinter, and 4H exclusion. Even if partner has a 6 count with no key cards, 5D should be a good contract, and if he has a key card, 6 stands a good chance, and with 2 key cards, 7 is nearly cold. But in standard, responder could have only 4 diamonds, so being cautious is a little more reasonable.

This last one is actually rather amusing to me. I was playing with Shaz last night and she opened a slightly different kind of canape 1H, promising 10-15 hcp and exactly 4H. RHO bids 1S and I have: void, AQ, Axxxx, Jxxxxx. Clearly I make a negative double and LHO raises to 2S. Shaz bids 3C! Would 4S now be exclusion? Or a splinter? Probably a splinter as 3S is basically a western cue. 5S as exclusion is a bit ambitious. Or is it? AK of clubs and heart K and a stiff diamond is all partner needs to the grand to be cold. I just bid 6C for win 11.47 as no one else bid a slam.