The only window screen material that is ferret proof is METAL that is
positively attached with staples, nail/screwed hold down strips, or
factory type intallation.
 
Plastic screen is NOT ferret proof.  Velcro attachment is NOT ferret
proof.
 
Debi Christy
Ferrets First Foster Home
 
Practical & easy training, care, & maintenance articles available at
http://www.geocities.com/ferretsfirst/
[Posted in FML issue 3801]