I learned many years ago, that there are just too many problems with
regard to a door to a ferret room, including pooping and the inevitable
digging (if they know there is something beyond, they will be relentless).
 
So what I did was to build a baricade that allows you to open and close
the door, but keeps the ferrets away from it.  You have to carefully step
over it all the time, but I don't mind.  It lets the door stay open all
the time, and if you are paranoid, you can close it to be sure.  It is
basically like this:
 
|
|
|              FERRET ROOM
|
|---------
          |
          |
 DOOR     |
          |
-------   |
--------------------------
 
The barricade is made from two 2' high by 4' long 3/4" pre-cut plywood,
and mounted to a 2x2 post which forms the corner.  Then screwed to each
plywood panel is a 2' x 4' x 1/4" material, but 6" off the ground to
increase the height of the barricade.  This is basically pegboard material
without the peg holes (learned that the hard way - nah they could never
climb a vertical peg board could they!?)
 
Where the barricade edges meet the walls I mounted these high-density
cardboard "corners" that are used to reinforce pallets of shipped goods
before they apply shrink-wrap.  This or something similar I have mounted
so that it starts just above the baseboard.  The plywood can then butt up
against the baseboard, and the other material is adjusted so that it rests
firmly against the wall.
 
Best of all this is a free-standing barricade.  It doesn't require
mounting into the walls, provided it is on carpet.  As standard practice,
I also buy carpet remnants to lay over the "real" carpet.  Very handy so
when it gets stinky or you move it can be tossed and you've saved the
expensive carpet.
 
Another thing I've done in the past when the ferrets were younger, is to
take a peg board and lean it on the door-side of the barricade.  My
ferrets would eventually tire of their "out time" climb up the ramp and
over the barricade, landing on a blanket, and then off to eat and sleep.
[Posted in FML issue 3684]