How to Square a Window Screen

Remove the screen from the screen frame. Use a slotted screwdriver or similar tool to remove the rubber spline that holds the screen to the frame. The spine is reusable if it is not rotten.

Inspect the screen frame. After removing the screen, the frame should flex back into place.

Measure the width and length of the frame using a tape measure. Cut a fresh piece of screen 2 inches bigger on all sides than the window frame.

Center the screen over the screen frame so that there is about 1 inch of screen overhanging the frame on all sides.

Insert the first piece of spline into the frame's channel using the screen roller. Start with the top side of the screen first. Take your time and carefully press the spline into the screen channel using the tool a little at a time until it seated in the channel.

Adjust the screen to remove any wrinkles or rolls. Install the two sidepieces of spline into the window frame. This part is critical to maintain a square frame. Start each piece and work them into the channels simultaneously, about 1 inch at a time. It is important not to stretch the screen during this process. Allow the spline to do its job. It tightens the screen during its installation.

Check the frame for square using a framer's square. If the screen is not square, remove the sidepieces of spline and start over, being careful not to stretch the screen too tightly.

Insert the bottom piece of spline. Allow the spline to remove any slack in the screen and check for square. Once the screen is complete and square, carefully trim away excess screen using a razor knife.