When we got our first fuzzies, they found small holes in the box spring cover, and found the soft underside a nice hammock to sleep on. They didn't appear to be in too much danger, but after a while, it got a might ripe and couldn't be washed. I thought about sealing the underneath with something stonger, but realized, that the cover was not needed for anything, it's just a dust barrier. I removed the bottom cover altogeather, and never replaced it. They were not happy that it was gone, but have found better places to sleep. The box spring is no longer a place where they can play, because there is nothing to climb into. ;) [Posted in FML issue 2029]