A man walked up to a farmer's house, and knocked on the door. When the farmer's wife opened the door, the man asked if she knew how to have sex. Not amused, she slammed the door. Again, the man knocked, and again, he asked the same question. Again, she slammed the door and screamed, "Get the hell away!"
Later, she told her husband of the incident. He said he would stay home the following day just in case.
Sure enough, the next day the same man returned. The husband hid with his gun while his wife answered the door.
When she was asked again if she knew how to have sex she said, "Yes!"
The man replied, "Great! Give some to your husband the next time you see him, and tell him to keep away from my wife!"