Perforce VCS checkout question, about branch setting

Hi all,

Can anyone tell me in TeamCity V4.5, how to checkout particular branch (path) of a client. (Do I have to set the client mapping to do that?)

How do I configure the Checkout directory? Can the checkout directory be the same as my perforce workspace?

In the webpage: http://www.jetbrains.net/confluence/display/TCD4/VCS+Checkout+Rules
How can I set up the "checkout rules"? What is the "+:src/samples=>./samples" means? Does that mean "src" is under current client direction?
It doesn't work when I set "+:lib/assembly=>Try2" (considering the current client is looking at "jack" folder), the command I set will still checkout everything in "jack" folder but not only the things in "lib" folder.

Thank you very much!!!