Thanks for the link that helped (mostly ;) for a problem I am trying to solve. My scenario is that I have a number of users that I only want to give access/show certain parts of the Content tree. I am able to lock it down as I want except the last item in both lists. I want to hide the top level folders of the tree just under the root. Is this possible?

User A logs in.
-they can read the Root of the site
-they can read Folder A (read only permission set)
-they can read and modify Document A1, Document A2 (read and modify permission set)
-they can see, but not read Folder B (I WANT TO HIDE FOLDER B FROM USER A)[/i]

User A logs in.
-they can read the Root of the site
-they can read Folder B (read only permission set, works)
-they can read and modify Document B1, Document B2 (read and modify permission set)
-they can see, but not read Folder A (I WANT TO HIDE FOLDER A FROM USER B)[/i]