I had the same problem.  My fuzzies got into the my sofa and a chair.  I
used a screen door material that is critter proof.  It contains no metal, so
it's pretty easy to handle.  My fuzzies have been scratching at it for a
week with no visable damage.
 
Joe
 
Phred ("Hey, what's this?!)
Timon ("What the?!  Come on, I got foam to shred!")
Hobbes ("I just saw 'The Great Escape.'  I got an idea.")
[Posted in FML issue 1477]