Bells are a great idea but if you have a door knob on the door they go out of save your money and tie a group of jingle bells to the end of ribbon. That's what we did with Lola and it works great, no need for barking when she has to go out, she rings the bell and we can hear it just about anywhere, if we don't come quick enough she bats the heck out of them. I also have a travel set of bells that I take with me when visiting family and friends, as soon as she sees the bells she knows it the potty door, sort of like a kitty with their litter box |