How to install dog door in glass?

Installing a pet door in glass is more complex than installing one in a wood or fiberglass door, primarily because of the properties of the glass itself. Tempered glass — used in most sliding glass doors and many exterior glazed doors — cannot be cut after it has been tempered. Attempting to drill or cut tempered glass will cause the entire pane to shatter. For tempered glass panels, the solution is to have the existing pane replaced with a new pane of the same specifications but with the pet door cutout incorporated before the glass is tempered. This requires ordering a custom glass panel from a glazing shop. Annealed glass (non-tempered) can be cut by an experienced glazier, but it is rare in modern exterior applications. An alternative approach that avoids cutting glass entirely is a pet door panel designed to replace the full glass insert in a sliding glass door track — these units fill the gap created by sliding the door partially open and require no glass cutting or modification to the door frame. These panel-style pet doors are widely available and can be installed by most homeowners.