I posted about using plexiglass, although I'm not sure its my idea you're
looking for....others posted as well.
 
We purchased a sheet of plexiglass cut specifically to the width of the
door frame, and about 3 feet high.  Then we purchased 2 narrow thin pieces
of wood, and nailed them, 2 on each side of the door frame, running
parallel with each other with about a quarter inch of room between each
other, kind of like train tracks running vertical.  The plexiglass slides
in and out of these slots to remove easily.
 
- mish
 
Michelle Matta
esgear Customer Support
[Posted in FML issue 2833]