Whew! Thanks for the explanation. You not only described a definition, but added some real life useage. I appreciate this. I guess, more patience on my part is needed, but I find that when I get confused and I don't deal with it right-away, I tend to get lazy. With 3D you can't afford to get lazy and I want to know this program. This message I will file in the layers section and it will probably be a key feature for me to know. Thanks for the help and you haven't heard the last of me. Phil