I had a problem with restricting my crew and wound up, of course, at the Home Depot. I got a large piece of plexiglass and cut it down to 2 inches large that the doorway to be blocked. I taped the edges that would be against the doorframe, and "bowed" it into the doorway -- VOILA!!! Ferrets can see out, but can't get out. You just have to make sure the piece is tall enough so they can't scale it. [Posted in FML 5720]