[pescetom]

I sometimes wonder if anyone in WBFland ever contested a defenders' agreement to lead 3rd or 5th below honour on the basis that the precise message conveyed is hidden from the declarer because of key information available only to the defenders (the length of their respective holdings)?
See WBF systems policy 2.6b.

Is there an equivalent prohibition in ACBL?

[mycroft]

How is opening leader's length "known to partner"? They can determine it from the auction, or surmise it from their holding. Equivalent(*) information is known to declarer.

Several interesting examples can be found at A night at the Crypto-Club. The relevant one to your question is "4th best against 3NT if we have 7 or fewer HCP in our hand, 3rd and 5th if more."

(*)In that your length or spots could lead you to believe partner doesn't have 5. Or the suits could be switched and then opener has the length or spots that makes 3rd more likely.

There absolutely is an equivalent prohibition: "Encrypted Signals are never allowed when leading, following suit or discarding". Interestingly enough, most (not the psychic control) of the rest of that document is perfectly fine on the Open chart, and anywhere that responder's calls are not regulated...

[pescetom]

mycroft, on 2025-October-31, 13:30, said:

How is opening leader's length "known to partner"? They can determine it from the auction, or surmise it from their holding. Equivalent(*) information is known to declarer.

(*)In that your length or spots could lead you to believe partner doesn't have 5. Or the suits could be switched and then opener has the length or spots that makes 3rd more likely.

I agree that there is no precise key. Hence a question, rather than an affirmation.
But the other defender knows for certain his holding and hence from the auction can often determine precisely.
The declarer is not in the same position.

I'm on the fence and curious. Never much liked the rule in the first place.

[Huibertus]

pescetom, on 2025-October-31, 12:05, said:

I sometimes wonder if anyone in WBFland ever contested a defenders' agreement to lead 3rd or 5th below honour on the basis that the precise message conveyed is hidden from the declarer because of key information available only to the defenders (the length of their respective holdings)?
See WBF systems policy 2.6b.

Is there an equivalent prohibition in ACBL?

It's just like 2nd or 4th (which is what 4th best really is). You simply can't lead the 5th from a 4 card, just as you can't lead the 4th from a 3 card. Declarer (and the partner of the lead) have to deduce if it was 5th or 3r best, just as declarer and the partner have to work out if a lead is 2nd or 4th.

Encryption is a different situation. It is a different carding agreement on the basis of information (as opposed to deduction) defenders DO and declarer DOESN't have. It was used for deciding to switch between high even en high odd distribution signals. For instance on the basis you lead Ace and King in a side suit, declare ruffs the second where dummy had 3. You'd then do HL even going forward in other suits, for the defender with an odd number of cards in the suit lead, and HL odd in case he had an even number of cards in the suit lead.

[mycroft]

"The declarer is not in the same position." Why not? Declarer's cards in the suit could easily be just as descriptive as third hand's.

As far as the prohibition on encrypted carding in particular, the issue (I believe, the restriction has been around far longer than I have been playing) is that the key is frequently not available (or discernable), and so other things (like tempo, manner, and placement) get used to resolve the "encryption". And if the tempo, manner, etc. get used, it can resolve the key information as well. Which, when it's something like "if I have the Ace of my suit", can be very useful information. And since it is not difficult post facto to create a legal rationalization for "how I knew", it becomes hard to catch unless you work out (that there is) the tempo-manner-anything key.

"We've tried playing 'odd with an honour, even without' signals for a few months and determined that we couldn't reliably resolve them. We've talked about this with a lot of other pros and they all say the same thing. How are *they* able to work it out so well, when nobody else can?" Well, as it turns out...