Hubby is an engineer and a little eccentric (Engineer and eccentric is redundant) We have cats and a dog. We have a cat door to our bedroom because hubby didn't want to leave the door open at night and of course the cats didn't want it closed. For years we had a screen door across the middle of our upstairs hall because two of our cats, Cleo and Fervor, would fight to the death if we let them. Later , after Cleo died we had a cat door in the screen door so the cat could escape the leader dog puppy, Penny, who managed to terrify Fervor. We have a wooden door at the top of the basement stairs with a cat opening in it so that the cats could go down to the litter box but the Leader Dog puppy could not get down to the cat food and litter box. Now Hubby is attaching a music box to the door that will play when we forget to close the door.