For example: AB (partners) lead trumps. They win the first three tricks, and show four by honours, and three more trumps remain in A's hand. Consequently, if AB win another trick, they win the game. Y or Z now has the lead for the first time. His lead should be from his weakest suit, on this principle: if his partner has not the command of it, or a successful finesse in it, the game is lost. Say Y leads, and Z wins the trick. Z should not return Y's lead, but should similarly lead his weakest suit.
For an illustration of this coup, see Hand XXVII.
TREATING LONG SUITS LIKE SHORT ONES, AND VICE VERSÂ.
It often happens towards the end of a hand, that an unplayed suit, of which the leader holds (say) four cards, can only go round twice, e.g., there may be two trumps left in in one of the opponents' hands. In such a case, if your suit is headed by queen or knave, you should treat it as a suit of two cards only, and lead your highest, as this gives the best chance of making two tricks in the suit.
In the reverse case, where a suit can only go round once, it is obvious that a small card should be led, so as not to tempt partner to finesse. Thus, holding queen and one small card of an unplayed suit, which you are about to lead, all the opponents' cards but one being winning cards, the proper lead is the small card.
For an illustration see Hand XXII.