Robocopy – Transfer Files Without Folders

I'm trying to use robocopy to transfer a single file from one location to another but robocopy seems to think I'm always specifying a folder. Here is an example:

robocopy "c:\transfer_this.txt" "z:\transferred.txt"

But I get this error instead:

2009/08/11 15:21:57 ERROR 123 (0x0000007B) Accessing Source Directory c:\transfer_this.txt\

(note the \ at the end of transfer_this.txt)

But if I treat it like an entire folder:

robocopy "c:\folder" "z:\folder"

It works but then I have to transfer everything in the folder.

How can I only transfer a single file with robocopy?