Example 1: Protecting a contract
You bid 5 and have already secured 4 tricks. Your opponent leads diamonds. You hold one low diamond and two spades including the ace of spades. The correct rules-first play is to follow diamonds if possible. Because you still have diamonds, you cannot trump this trick. After you lose that trick, you keep the ace of spades as a guaranteed converter later. The rule may feel restrictive in the moment, but it actually protects game balance and skill expression.
