Determine the shape of your window. Window grilles fit standard rectangular windows or they can be designed to fit the following window shapes: segment, quarter round, quarter radius and elliptical.
Measure the window. Take your time and measure twice. If you get an incorrect measurement, your grille won't fit properly.
Fit the grille into the window. Place the grille on the inside of the window and push the pins in to secure it.
Secure the grille to the window. Glue the grille to the window to keep it in place for years to come.