n00b problem with svn and finding a file

[Jim Kissel]

I'm looking for the file that is the source for

New_to_Ubuntu -> Basic computer skill -> Desktop Sessions -> Locking 
Your Screen

or the on-line version:
https://help.ubuntu.com/7.04/user-guide/C/lock-screen.html

I've so far downloaded via svn the document tree for 
trunk/feisty/edgy/dapper but I still can't find the user-guide sources. 
  Just need a little help to get started. (please)