Years ago I taught a dog to knock down the lever type handles. He taught other dogs and cats. When I moved house the cat went all around the house even if the doors were shut by opening each door. In the end I changed handles. But I had a new front door with a lever, the cat used to pull the lever down then slide off to make a clang sound to let me know when sh wanted to come in. My mother always said it served me right for teaching the dog. .my present cat lives half out and in. If she can't get in she just makes a sound and 3 dogs barking soon get attention. She comes in and sleeps in one of the dogs beds who tries to get in. Clever to their own ends.