You know how they make that invisible fence for dogs? Like those ones that they put stuff in your lawn and then your dog gets a collar that goes with it and then they can't run out of your yard? Do they make something like that for cats?? TIA
You could try the electric fence, but you have to train them by letting them get shocked first. I don't like the fenses, but since you can't put an enclosure up, your options are limited.
Do you have an actual fence? like a real wooden one? or is your yard just open? there was a thread here on this... i think it's the indoor vs. outdoor one...
there were a couple of links there for fencing/enclosing options...