Door vent glass on vehicles may be a side window on each side of the car just forward of the rear window of the vehicle. Only some cars have them. In some cases the fixed quarter glass may set in the corner of the vehicle. Door vent glass is also sometimes called a valence window. The door vent glass may be set on hinges and is then also knows as a vent window. Most often found on older vehicles on the front door, it is a small roughly triangular glass in front of and separate from the main window that rotates inward for ventilation.