In days of old, when knights were bold, this particular knight was leaving for a crusade and called one of his squires: "I'm leaving for the crusade.
Here is the key to my wife's chastity belt. If, in 10 years, I haven't returned, you may use the key as I'm sure she will have needs."

The knight sets out on the dusty road, armored from head to toe. He takes one last look at his castle and sees the squire rushing across the drawbridge, yelling, "Stop! Stop! Thank goodness I was able to catch you. This is the wrong key."