[arepo24]

When I asked my P for a Blackwood response (4NT) he replied 5H. I assumed he had 2 Aces and I passed.
When he laid his hand down he had 1 A and a void.
Is this legal? Does it need to be alerted?

[pescetom]

 arepo24, on 2020-August-29, 09:41, said:

When I asked my P for a Blackwood response (4NT) he replied 5H. I assumed he had 2 Aces and I passed.
When he laid his hand down he had 1 A and a void.
Is this legal? Does it need to be alerted?

Both the ask and the answer are artificial bids, so on BBO both should be alerted with the agreed meaning.
It sounds like you did not have an agreed meaning with P here.
It is not illegal to have a bad agreement, or none at all, or to deviate from an agreement.
Showing a void as an Ace or Keycard is not a good idea and should certainly not be done without agreement.
I think the majority treatment is to not mention the void, which is a good choice for beginners.
In Roman Keycard Blackwood some show the void by bidding 5N with an even number of keycards plus undisclosed void and 6X with an odd number of keycards plus void in suit X (or higher suit if X is trumps).

[arepo24]

 pescetom, on 2020-August-29, 09:54, said:

Both the ask and the answer are artificial bids, so on BBO both should be alerted with the agreed meaning.
It sounds like you did not have an agreed meaning with P here.
It is not illegal to have a bad agreement, or none at all, or to deviate from an agreement.
Showing a void as an Ace or Keycard is not a good idea and should certainly not be done without agreement.
I think the majority treatment is to not mention the void, which is a good choice for beginners.
In Roman Keycard Blackwood some show the void by bidding 5N with an even number of keycards plus undisclosed void and 6X with an odd number of keycards plus void in suit X (or higher suit if X is trumps).

Thank you. He was a BBO player and I never played with him before

[johnu]

 pescetom, on 2020-August-29, 09:54, said:

Both the ask and the answer are artificial bids, so on BBO both should be alerted with the agreed meaning.

Of course, since the 5♥ bidder was the partner of the OP, the OP would never know the bid was alerted.

[johnu]

 arepo24, on 2020-August-29, 09:41, said:

When I asked my P for a Blackwood response (4NT) he replied 5H. I assumed he had 2 Aces and I passed.
When he laid his hand down he had 1 A and a void.
Is this legal?

Is it a legal bid? It is not prohibited by any bridge organization I know of, so yes, it is legal bid. Is it a correct bid? I have never seen anybody (or read any books where this is advocated) use a 3 step response to Blackwood to show an ace and a void, so I can 99.4% say that this was not the correct bid. If you had a specific partnership agreement ( don't know anybody who has this agreement), then it could be the correct bid.

There is actually a quasi-official set of responses that show a void in response to Blackwood. For an odd number of key cards and a void, you jump to 6 of your void if the void is in a suit below the trump suit, or 6 of the trump suit if the void is in a higher ranking suit.

[blackshoe]

Quasi-official? Didn't Kantar talk about it in his five RKCB books, the last of which is Roman Keycard Blackwood: The Final Word?

[johnu]

 blackshoe, on 2020-August-30, 12:52, said:

Quasi-official? Didn't Kantar talk about it in his five RKCB books, the last of which is Roman Keycard Blackwood: The Final Word?

Believe it or not, I don't own and haven't read any of those books.

[mycroft]

You are allowed to bid whatever you want, even if it violates your agreement, provided partner is as confused as opponents.

You are allowed, in most regulatory environments, to have any responses to Blackwood you want. You have to explain it to the opponents correctly, of course.

Alerting depends on your regulatory environment, on BBO I would assume that I would self-alert that "2 first round controls", same as I would Alert mine "2 keycards for <suit>, no <suit>Q" or "2 aces", depending on partner.

A lot of questions you have asked seem to assume that there is One Correct Answer to everything in Bridge. That is not correct - there is Always More Than One Way To Do It (tm Larry Wall). There are better answers and worse ones, and ones that work on this hand (but are worse over all), and ones that partner can remember, and ones that are what partner remembered of what his teacher taught, whis is what she remembered of what she was taught, which was...

A standard way of showing (useful) voids is to use 5NT and the 6 level bids below the trump suit to show even/odd KC and void location. Partner is supposed to be able to figure it out. But it's your responsibility to have an agreement with your partner.

If it's a pickup partner - well, that happens. That doesn't mean There's One Right Way.

[barmar]

 johnu, on 2020-August-31, 01:55, said:

Believe it or not, I don't own and haven't read any of those books.

The void-showing responses are also described at many websites that explain Roman Keycard Blackwood.

The main idea is that it's *not* standard to treat a void the same as an Ace in the Blackwood responses.