knots and which end is up

On a timber, how can you tell by the knots and/or other feature which end is the butt and which is the top?
I have heard that bark developes in the butt end of the knot, but in my experience with Douglas Fir the bark in the knots can contradict eachother.
-Collin

Hello Collin,

A while back I read Identify Wood, by R. Bruce Hoadley.
I remember some talk about just that. It's a neat book, and at any rate, helped me identify mystery woods with a ten power hand lens.
Good luck,

Zach

Thank you Zach, I will give that book a look.
-Collin