I also use heavy ball chain (Ace hardware) for collar with small bell
(I use a 1cm bell with slot filed bigger than normal).
 
I would suggest making a ferretlock for your door.  Mine is a thigh-high
two-sided box of cherry paneling around the corner in which the door is.
Mine is hinged at the corner for storage (if ever need be for moving or
something) and finished on the corner with nice moulding.  I have chicken
wire under the edges near the wall u-nailed into the carpet to prevent
digging.
 
top view (looking down at floor):
 
DDDDDDD
     K |c
       |
BB     |
--------
c
 
D = door, K = knob, else = paneling, BB = box, c = patch of chicken wire.
 
You might wish to put a box on the other side of the ferretlock so
your ferrets can get back over if they scale it when you aren't home.
 
Using a ferretlock, your ferrets will not be able to escape when you
go out the door.
 
I found cereal all over the floor the other day.  Turns out Dors went
into the kitchen cabinet, up the back of the kirchen drawer, then she
pushed open the drawer and went out on the counter, then pushed the box
off onto the floor and went back down to root around in it.  There is
nothing dangerous in any of these places (I hope).  There is the slight
danger she might fall off the counter.
 
Todd Cromwell
Dors (novia) and Seldon (cazador de suen~o)
TX
[Posted in FML issue 1227]