I don't have any raccoons, opossums or squirrels in my immediate area,
so I don't know if they would work for that.  I suspect they probably
would work for raccoons and possums, because they seemed to be about
large cat size where I used to live.  Squirrels might be able to
climb the fence planks themselves and still get over the drain
pipe on the top, just as I've seen them climb birdfeeder poles.

I guess something as large as a coyote, which could hang its whole
paw over top of the fence would need the roller action, whereas the
cats only need something rounded on the top that their claws can't
grab into.  The plastic corrugated drain pipe (looks something like an
oversized black vacuum cleaner hose) was so easy and cheap a solution,
I wish I'd heard of the KittyKlips sooner.

Most of the time, my cats and I only saw the invaders from the window,
when they were inside, but a few times they came over when my cats
were out, and I chased them with the hose sprayer.  Gideon (17 yrs,
Maine coon) is so hairy and sheddy that when young invading tomcat came
at him the one time, fortunately all he got was mouthfuls of hair,
and slobber on Gideon's fur (good thing I hadn't had him lion cut),
but it had intimidated him from spending as much time in his yard
as he always liked.  He's seemed nervous about staying out when I'm
not out there, but wants to just do a quick patrol of his space.
Three or four weeks now without any invasions, and I think he's
starting to relax more like his old self before the invasions, and
lie in his grass.

I have bookmarked Coyote Roller and will look into it.  Meanwhile, another
excellent commercial product is Cat-Fence-In, which keeps pets in and
pests out (the combo model).  Though, I must say, Cat-Fence-In didn't hold
up to determined raccoons when we used our cat-proofed backyard to house a
feral cat who had to be fed in the enclosure.  Even with her food enclosed
in a feeding station, the raccoons detected it and beat their way in to
mooch.

Sharon Talbert
Friends of Campus CAts