Before Bradley was big enough to use the doggie door he learned to ring the sleigh bells that hang on both the front and back doors. I was intended for him to use these bells to let us know when he needed to go out to potty. However, sometimes he rang them to go out and get a drink, find a stick or torture the cat. But the point is that he knows that ringing the bell opens the door. By our front door stands a little end table where upon I keep the leashes. There is a little red box on the lower shelf where I keep the harnesses used to seat belt them into the car and to take walks. Bradley is so funny in that when I go to get the harnesses out of the box, he rings the front door's bells and then sits waiting by them. It's like he's saying "I'm ready, let's go." This week when we were getting in the car to go to school (not going for a walk) he rang the bells by the front door while I tried to harness him. Then when he was spastically waiting at the car door I swear he was thinking "Where's the bells to open this door."
I included some pictures so you didn't just have to visualize the scene. BTW Brodie is a camera hog. I was trying to take a picture of the end table by the front door. Even though he was working on a nap, he had to get up and lay down in the shot. What a silly dog!