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]