Connie,
 
I use a piece of hardware cloth under my refrigerator to prevent the
fur-rats from getting under it for a nap in the insulation.  Hardware
cloth is like chicken wire but the holes are much tinier.  By clipping it
and folding it down a couple of times into a shape that fills the area,
you end up with lots of little spikes poking out the end.  No weasel is
going to let his nose get poked by trying to get close enough to dig/pull
it out.  Even my tiny mouse-like girl who fits into every possible crack
and crevice hasn't broken through this barrier in two years.
 
Good luck,
Debi Teter
[Posted in FML issue 4803]