I am assuming that you are trying to clamp down the litter pan in the cage
and not out in your hallway or room somewhere in the house ... if so ... I
have the perfect solution and it cannot be budged - not even Jaymes my huge
4.5 pound ferret can move this (he certainly tries though let me tell you!!)
 
I have 3 of the "corner" type of litter boxes and I have punched holes near
the top (one on each side) and near the bottom by the sides (one on each
side)
 
sort of like this:
 
o    o
       o      o
 
 
o   o
       o                     o
 
I am really bad with this kind of thing - anyway, take some pretty thick
wire and run it through the holes and through the wires of the cage and
voile!  Ferret proof litter pan!  (it took me a while to get this working
so be patient - you have to hit all the right angles!)
 
Good luck
 
Marion
[Posted in FML issue 2292]