A knight is called to war by his liege
Before he leaves he puts a chastity belt on his wife, locks it and trusts his stewart with the key.
Just as he was about to leave the stewart comes running towards him
"Sir, you left me the wrong key!"
I was going to buy a chastity belt until I checked the reviews online. Customer satisfaction was terrible.
If I'm honest I can do without a chastity belt.