The scenario is appending part of a path (i.e. several levels of folders) from a path that does not require URL encoding onto the end of one that does, or vice versa.  i.e. you know that (for example) http:// can't accept several characters that other filesystems are quite happy with.  Thus, you wish to convert those paths (on a folder by folder basis) so that you can still hit the files on the other end once the path is fully constructed.  Path substitution when using webdav I believe is the scenario that @arnova is doing this under.

I'm sure @arnova can construct an specific example where this needs to be done.