What's the meaning of the "Override working folders" checkbox in Visual Source Safe?

"I guess you're talking about this:

From the Visual SourceSafe help file:

Override Working Folders (project-level Check In only)
Overrides the working folder set for
the subprojects involved in a
recursive operation. This is useful if
you have some shared files checked out
in more than one project, and want to
check them all in at the same time.
Available only when you select the
Recursive check box.

It means that if you have set different working folders for different sub projects, the system overrides that and acts recursively as if only the top folder (on which you perform the action - check in, check out or get latest) has a working folder, and everything beneath it is also relatively beneath it on disk. Hope this makes it more clear.

By popular demand: an example:

If you have the following tree in Visual SourceSafe

Main project ==> working folder = c:\MyProject
|-- SubProject1 ==> working folder = c:\SubProject1
|-- SubProject2 ==> no working folder

And a corresponding tree on your disk:

c:\
|-- MyProject
| |-- SubProject1
| |-- SubProject2
|-- SubProject1

So when you do a Check-in on the MyProject level and you don't check the ""Override Working Folders"" checkbox, then the files to check in will be taken from:

c:\
|-- MyProject
| |-- SubProject1
| |-- SubProject2 <-- here
|-- SubProject1 <-- and here

When you do check the ""Override Working Folders"" checkbox then the files to check in will be taken from:

c:\
|-- MyProject
| |-- SubProject1 <-- here
| |-- SubProject2 <-- and here
|-- SubProject1"