No its not car doors or the tail gate on your truck. Its not even from falling on your patoot.
For the surprising answer We turn to an old friend who really knew his stuff.
Perhaps this will save someone's favorite fly rod.
http://www.flyanglersonline.com/alcampbell/ac050602.php
You will find the answer in Error #1
Surprised? Me too. hoo wood a thunk it.
For more flyfish wisdom from AL Campbell go to the home page. Click on features, click on Al Campbell . Pick a topic and read on. Super interesting stuff.