Measure the height and width between the inside edges of each sash, or window frame. Record the measurements as well as the model code which is etched in the glass at the bottom corner of the window. Take the measurements and model code to your local home center or window dealer so the proper size grille can be purchased or ordered. This model code will also help you determine what type of fastener clips you need.
Start at one end of the top inside edge of the window frame molding, and locate the first grille notch. Attach a fastener clip to the installation tool and slide it into the notch. Repeat the process across the edge of the top frame and around the entire window.
Mark the locations on the window frame where the fastener clips insert if your particular model has no notches. Do this by placing the grille against the window and lightly marking with a pencil the points where each of the ends meet the frame. Slide the fastener clips into the frame at the marked points using the installation tool.
Set the grille against the glass with the bottom ends touching the inside bottom of the window frame at a very slight angle. Line up the bottom ends of the grille with the corresponding fastener clips. Push down lightly to snap the bottom ends into place.
Gently push the top ends of the grille into the fasteners located on the top of the window frame. Attach the grille to the fasteners along the sides to firmly secure it in place.