Chris -
I use a large plexiglas sheet on the ferret room. It was cut 1/4" larger
than the opening (intentionally) and I used a router attachment to make a track
(or groove) that holds it in place. It's heavy enough that they can't move it
up and it's clear , which allows my cats to watch them from a safe distance.
a screw at the top of the groove (on both ends) is extra insurance.
Roger McMillian    Owned by Cinnamon Bear, Megabyte, Tribble, Heidi & Sneakers.
 
[You groove the door frame?  I'd be tempted to produce a u-channel molding
that could be screwed to the trim instead.  On the other hand, you should
see my child gates. ;-)]
 
[Posted in FML issue 0355]