A method to prevent carpet damage from both causes that I have used for some
time is to use scrap pieces of vinyl from a local floor covering store.  I
cut a piece approximately two feet wide and one foot longer than the doorway
is across.  Then I cut out pieces at the center of both ends that are shaped
to go around the door jam.  In the end you have something like a very fat
"H".
 
The vinyl piece should lap in front of the walls on either side, at least
six inches, and behind the door it should extend to the corner if there is
one.  It should lap ten to twelve inches into the rooms on either side of
the doorway to discourage them from nosing under the vinyl and digging the
carpet.  Because the notches on the ends sort of lock it in place, it tends
to stay put.  (I would attempt to make a picture, but I know it would only
confuse you more, as my computer art is lousy.  If you want to e-mail me
with your street address, I'll send you a picture.)
 
This doesn't stop the digging but they dig at the vinyl instead of damaging
the carpet.  They soon tire of this, realizing the futility of it, I think.
If they poop in the corner, at least, it will now be on the vinyl.  I
usually tape vinyl pieces in corners or layers of newspaper for easy clean
up.  After all ferrets are only 'human' and they can't always make it to the
litter box in time.
 
It works for me!!!  Hope you will try it.  --- Trish
[Posted in FML issue 1484]