Thank you. I have selected Ron's answer as I am a complete router-newbie and I found his approach was more enlightening in a practical sense, but I appreciate these links and added info. Very good to know! :)

Thanks, I accidentally mistyped my question, but your answer was clever enough to cover what I wanted to know. I have 2 questions, out of your explanation: 1. What is considered an "unknown *cast" 2. Why can it kill the box?