we have dogs. that keeps them away.
Ive heard this kind of fence will help keep them in. Turned around it should help keep them out. (I am not saying you should buy this fence it is just for the pic to see it.)
http://store.purrfectfence.com/Prod...ANDING&buttonOutdoorCatEnclosuresFreestanding
if the fence curves toward them they don't think they can jump it. Not sure if you can do something like this to help. Your post didn't say what you were trying to keep them out of.
another option may be a motion detecting sprinkler. look up a scarecrow sprinkler.
hope this helps.
Holy crap, that fence. Why don't they make livestock fence like that? Can you imagine the coyotes, coons and possums that would keep out?