On warm summer nights when you want to keep the patio door open for ventilation, the patio's sliding screen door is the only thing between you and a world of mosquitoes. If a lot of people come through the door, the fragile roller mechanisms can fall out of adjustment, or the screws on the corners of the door can loosen, causing the door to eventually get stuck or fall out when you try to slide it. Screen doors are not difficult to adjust, and if one of the rollers is broken, it is not difficult to replace.
Remove the screen door from the frame by grasping it on both sides and lifting the rollers off the lower track. Angle the bottom toward you and lift it a little further to disengage the runners on the upper track, then pull it out of the doorway.
Lay the door on a flat surface and tighten the screws in all four corners. When they are loose, the door can sag and the runners can lose contact with the upper track.
Adjust the height on the rollers on the bottom of the door by turning the screw next to each one clockwise with a screwdriver. Tightening the screws will force the wheels farther out.
Replace either of the wheels if it is chipped or broken. Push in the clip on the side of the door and pry out the wheel with a screwdriver. Take it to the hardware store to find a suitable replacement, then snap the replacement roller in place.
Lengthen the door if it is slightly too small for the frame. Loosen the screws located on the edges of the door near the top and bottom rails. Slide the rails out to make the door longer, then tighten the screws. The screen will stretch enough to allow you to make this minor adjustment.
Straighten the runner on the top of the door frame with pliers if it is bent.
Replace the door by hooking the upper runner to the track, lifting the bottom of the door over the lower track and setting it down so that the ridge on the lower rack fits inside the grooves in the runners. Be sure the runners are on the ridge, or the door will fall out again.