The hangout

Hello
My girlfriend has three indoor/outdoor cats. Other cats from the neighborhood sneaks in at night and during the day and hangout, eat all the food...one night I came downstairs and walked into the living room and I saw almost every cat in the neighborhood laying around with there feet up after eating a heavy meal. I saw stray cats, well-groomed cats, alley cats, bobcats When I turned on the light thinking they will run out the house, they all just looked at me and told me to turn that dang light off. No I'm just kidding the light and the bob.

But what can we do to keep the neighborhood cats out of the house?

Keep your cat in and get rid of the cat door. That's the cheap and easy fix.

More expensive; get an electronic door that only opens for an ID tag on your cat.

You can also build an outdoor cat enclosure for them to go into from the cat door. This will keep your cats safe and will prevent the other cats from coming inside. The cat enclosure will still allow your cats to go outside, but they will not be able to roam

If you have open windows,make sure there is a screen.

A few yrs ago,we would leave the windows open and had no screens and stray tom cats would be coming in and spraying.I remember several times going down to the basement and having the crap scared out of me by some tom cat!

Don't leave food out in the open.

Close off the open door. Getting rid of the free food might help, but randoms will probably come in anyway to be like cats are, curious. Getting an electronic cat door that opens only for your cats could help, but other cats can still get in by following them. Your best bet is to keep them inside or build a pen. Or get used to your house being a hangout, your cats probably do the same with other homes too.

Thanks everyone for your solutions. I think I'm going to build a cat enclosure. I have been researching on different kinds. I really like the purr-fect fence, but it is very expensive. Some enclosures simply look like chicken coops to me. Does anyone know of any schematics or plan designs of enclosures I can get my hands on?
Thanks

Just my two cents - my father-in-law was having this same problem. He had two cats - Spike and Rosie (mother and son). Rosie was a former feral and she spent most of her time outside. Whilst out there, she picked up a male friend (she was fixed). They roamed the neighborhood together, probably terrorising all the birds. Anyway, Rosie started bringing her little friend in with her - we called him Mr Fluffy - and he would terrorise poor Spike (plus eat all the food). It got to the point where he would hang out in the house even if Rosie wasn't around. So, my f-i-l went and got one of those electronic cat flaps with those id's for each of the cats and the problem was solved. Rosie and Mr Fluffy did all their socialising outside from then on.