Double Image features an option that allows you to backup Windows Offline files. Offline files are files or folders declared offline on a host (local) computer running Windows platforms that are networked with the host.
Offline files give you the ability to work with network files when they are not connected to the network. For instance, Offline files are useful when you're working on a laptop remotely or over a slow network connection.
Suppose you disconnect your laptop from the network, and while you're disconnected you update files declared Offline on your host computer. When you reconnect to the network, Windows synchronizes the Offline Files by updating the host files from the matching laptop files. Then, Double Image backs up the updated files.
Following is an example of folders and files on the remote machine, after declaring them to be Offline Files.
Notice the down arrow in the folder icon, indicating off-line folders and files.
Also See Windows Help for further details describing Offline Files.