Vent windows are auto glass windows that are mounted on the sides of vehicles, usually next to retractable windows. Vent windows differ from a door glass and quarter glass when they can tilt open. In the last 10 or so years, almost no vent glasses open on passenger cars. Now the purpose is cosmetic or to make rear door glasses able to roll down farther than they would without the vent glass. Vent windows are in rear and front windows, or sometimes in front of the front doors.The vent window was created by placing quarter glass on a hinge, to allow ventilation of the passenger cabin, back when cars did not have air conditioning. The quarter glass vent window has since gone out of style in automobile design.