Lately I've had some timely questions about a practice that seems to have become common especially among novice and intermediate players. I had an email from a director in Palm Desert who has noticed this practice, and a question about it at my most recent summer bridge class.
Players, as dummy, have been routinely reminding declarer which hand they're in. The common thing is tapping the table to remind declarer that she's "on the board."
When it was brought up in class, I said, "Well it has to stop!" which got a bit of a chuckle.
Let me go into detail about dummy's rights and privileges. They're quite explicitly called out in the Laws of Duplicate Bridge.
First, there's Law 42 B. "Qualified Rights" paragraph 2.:
2. He may try to prevent any irregularity.
That means, if dummy notices declarer about to play a card from the wrong hand, he can try to correct it before he does so. That has to be balanced with Law 43 A. "Limitations on Dummy" paragraph 1.:
(c) Dummy must not participate in the play, nor may he communicate anything about the play to declarer.
The laws also have a specific remedy if such action is taken. Law 43 B. "If Violation Occurs," paragraph 2.:
(a) warns declarer not to lead from the wrong hand, either defender may choose the hand from which declarer shall lead.
There it is, in black an white! So yes, it has to stop. But if it doesn't, then you have a remedy! Call the director to the table, and he will permit either defender to designate which side declarer must play from. (Which defender? Whoever speaks first. They don't get to discuss.)
There are other very good points related to dummy's rights and limitations in Laws 42 and 43. I highly recommend cracking open a copy of the Laws of Duplicate Bridge and reading those two laws. It will take you about 30 seconds. You'll be amazed what else you'll discover just bouncing around the pages.
If you don't have a printed copy on hand, you can download a PDF for free from the ACBL at this link.