I was in Sweden last September and visited with ferret people there.
They don't use cages for their ferrets at all.  One lady I visited has
her front yard fenced with wooden pickets set close together so they
can't squeeze through.  Plus she has wire at the bottom so they can't
dig out.
 
At a place called Skansen in Stockholm, they have a zoo area with ferrets
on display.  This is outdoors with a wire fence around it.  Made of, I
think, 1/4 or 1/2 inch mesh.  It looked galvanized.  Around the top, to
keep them in, was an overhang made out of metal.  Like you might see on
metal barns.  It stuck out about 6-8 inches at a downward angle.  I was
there at feeding time and they were fed raw bacon, yuk!  They called them
polecats, but they looked just like our ferret pet variety.
 
I took some pictures because I wanted to do something like that for my
guys.
 
Be careful when they are outside.  Their scent seems to attract bees and
hornets, etc.  So, here in Minnesota, we also use bug netting to protect
them.  And then you have the added worry of fleas and ticks if they are
outdoors.
 
Good Luck,
Liz
...in the Company of Ferrets, Inc.
www.ferretasylum.com
[Posted in FML issue 4881]