-When a "pad" file is used, it is updated as an "ar" archive where each
-write event is a new member appended at the end. The "pad" member has
-two additional, newline-terminated text lines with the insertion
-position and the member size (ascii decimal digits), before the actual
-insertion event content.
+Unmount is done with "\fBfusermount -u\fR \fImountpoint\fR" as usual.
+
+.P
+\fBUsing overlay file\fR
+
+.P
+A fusefile mount with an \fIoverlay file\fR is writable regardless of
+the fused fragments, but all updates are written to the overlay file
+instead of to the fragments.
+
+ $ fusefile -oallow_other -ononempty disk.raw \fB-overlay:today\fR disk.raw
+
+The overlay file ("today" in the example) contains all changes to the
+original file ("disk.raw" in the exmaple). It also contains a marker
+table at the end, as if appended to the fused file. This part of the
+overlay file is outside of the fused file; it consists of an element
+count followed by pairs of byte addresses to mark out which regions
+have been written into the overlay file, and the marker table is
+maintained so that adjoining regions are collapsed.
+
+That means that an overlay file may be reused to later re-establish
+the same fused file with overlay as previously, to continue capturing
+more changes.