Attention Before Purchase: Our glass dog door has a fixed - swing mechanism. If it's installed on the left side of the glass door, it can only open inward. If installed on the right side, it can only open outward. This is non - adjustable because of the design structure. Also, note that installation demands using a drill to bore holes in the door frame. Openable Design: Our dog door for sliding glass doors opens inward to maximize limited space, making it easy for people to move items in and out of the backyard.