Power Pet Fully Automatic Patio Pet Door Turns any sliding glass door into a fully automatic pet door Pet door insert easily fits into your sliding glass patio door track Motor driven vertically-sliding door is activated by MS-4 ultrasonic colla Directional sensing system opens the door only when your pet is on a direct approach, not when he is just wandering by or sleeping next to the door 4-Way access control lets you select from In only, out only, Full Access or closed and locked