Riddle: A woman is in her hotel room and heard a knock on the door. She opened the door to see a man whom she had never seen before. He said "Sorry, I have made a mistake, I thought this was my room." He then went down the corridor and into the elevator. The woman went back into her room and called security. What made the woman so suspicious of the man?
Answer: Because you don’t knock on your own hotel room door!