My aunt is moving into a new house with a fenced backyard and a dog door. She is excited about this, since it will give her dog new freedom, but she is concerned about her cat, Sidney, getting outside as she has always been an indoor cat. I told her that I thought there was something you could attach to the top of a pre-existing fence to keep your cat in the yard (and to keep other cats out) but when I looked at some threads, I could not find a link. (I found threads containing sites where an full fence is available, which is not what she needs.) Can anyone help me out on this?
Thanks!!!

When I saw the title, I got the image of your cat fencing with another cat... y'know, with swords... :P

Bottom of the fence is just as important--they can squeeze through. Chicken wire buried about 6 inches should do fine, though.

Man, I hadn't even thought about the bottom of the fence! Thanks, Callista:)

Here is one alternative. :)

http://www.catfence.com/pictures.htm

I use the fence in the link above. It's great. No escapes in 10 months of use. The company is great for answering your questions as well.

If you don't have the money to purchase something you can build your own pretty easily. http://www.feralcat.com/fence.html

I just used some thin metal rods (free leftover chunks) connected to the top of the fence with cable ties and then rolled aluminum screen door mesh across it and attached with smaller cable ties to the top of the chainlink. On the bottom I sunk reebar (again free leftover chunks from a construction company) into the ground every few feet and attached the bottom of the fence so it can't be shoved out where it would allow them to slip under.

I use the fence in the link above. It's great. No escapes in 10 months of use. The company is great for answering your questions as well.

Has it worked well for keeping critters out as well as in?

Thanks for the links! I'll pass the info onto her about the cat fence as well as needing to bury chicken wire at the bottom of the fence:)

Yes, we've had no problems other than squirrels, which go over the roof and leap into the trees. Then again, the squirrels offer TERRIFIC entertainment for the cats and maybe one day they'll "get lucky!" heheheh