A "box" serves both as a directory and a file, depending on what you "select" (the box itself or its sub-box).
* If you select a non-existent box, a new one is created.
* You can "copy" a box into another. If the target box is expected to be of a different type (unclear how this is known), the copying process may involve conversion.
* There is an "antibox" that you can copy to the target box, in order to remove the target box.
I found the following: http://lsub.org/ls/projects.html