I back my car into my garage. I set the sensors at the height that insures the sensor's line across the door "sees" the point of the car front last as I back in. For instance, the lower splitter does not stick out as far as the front bumper fascia. So I want the line across to break the bumper/fascia. This prevents the door from starting to close and does not start until I have backed in far enough.
I suspect your next question is, how do I know when I have back in just far enough? I installed a
motion activated dual laser parking aid on one side of the garage and point one of the lasers across the opening at the same height as the sensor's line. In order to see when the laser light crosses in front of the car, I use a small compact mirror mounted (with double sided tape) on the garage wall. The mirror reflects the light (a red dot) back across the opening at an angle up to a point where is hits the wall about 4 feet above garage floor. Since its reflected across the opening, hits a mirror and comes back to the same wall where the laser light aid is mounted, I can see it at driver height easily. When I see the red dot, I know I am safe to close the door and the door will absolutely miss the car . I use the other light on the aid, to point across the opening and above the mirror so that I know the aid's laser light is still turned on and the motion detection timeout has not occurred yet. Once in a while, I am slow to back in and the timeout occurs. I just pull forward out of the garage and back in again to trigger the light aid to turn on again.
I also have another mounted on the ceiling pointing down to two spots on the dash. When I see my relative position as another way as the ceiling mounted laser light's red dot hits the place on the dash that I am familiar with.
(More than you wanted to know?)
