We have had some recent unintended calls and plays which have indicated that players are not familiar with these rules. Basically, you can correct a slip of the fingers or tongue, but not a slip of the mind. I will give some examples to illustrate the difference.
1. You decide to open 1 Spade. You place the bidding card in front of you. Some time before your partner bids, you look down and see the 1 No Trump card. You immediately say "Wait, that's wrong." and call the director. You explain and he allows you to withdraw the incorrect 1 No Trump and substitute the correct 1 Spade. If LHO has called, he may withdraw his card and substitute another without penalty.
2. You open 1 No Trump and your partner responds 2 Hearts. Hearts are your weakest suit so you rebid 2 No Trump. You then realize that your partner was transferring to Spades. You immediately say "Wait, that's wrong." and call the director. You explain and he rules that your bid stands. You meant to bid 2 No Trump and then remembered the transfer. A slip of the mind.
3. You are defending against 4 Spades. Your partner plays the Ace and King of Hearts and you play high-low. He leads a low Heart, the board covers, and you trump with the seven of Spades. Declarer stops to think and you look down and see the 7 of Clubs. You immediately say "Wait, that's wrong." and call the director. You explain that you meant to play a Spade and pulled the Club by mistake. He allows you to make the substitution. The 7 of Clubs will be a penalty card.
Note that if you played the Club, thinking it was trump, and immediately remembered that Spades were trump, the play would stand. A slip of the mind.
Note that if you played the Club, thinking it was trump, and immediately remembered that Spades were trump, the play would stand. A slip of the mind.
4. You are the declarer and you must get rid of a loser in your hand to make your contract. You decide to trump losers in dummy's long Heart suit until the Ace falls and you can discard your loser on the Heart King. You play a low Heart from the board and trump it. You return to board, lead another Heart and trump it, dropping the Ace. You return to board, lead the King of Hearts and trump it. You immediately say "Wait, that's wrong." and call the director. You explain your plan and that you meant to throw the loser on that trick. He rules that the trick stands since you meant to play the trump and then realized that you'd momentarily forgotten your plan. A slip of the mind.
You can see that the difficulty is for the director to read the players mind and know what really happened. Many directors don't enforce these rules at all. They say that they can't be sure, so they forget the whole thing. Since it is director's job to ensure that, as much as possible, results reflect bridge skills, he must try to limit "windfall profits" caused by other factors. He must do his best with these rules.
