Keep those pesky flies and mozzies outside where they belong. If your windows are not of a standard size, you may not be able to find an insect screen to suit. Make your own with aluminium framing shaped to take corner joiners and spline grooves for securing the mesh.
Gather your supplies:
Flyscreen mitre box (designed for screen framing); flyscreen frame channel; insect screen mesh; hacksaw; metal file; corner joiners to suit frame (4 per screen); spline to suit frame and mesh (some stiffer meshes need a smaller spline); spline roller; utility knife; catches and clips; tape measure
Measure up opening by taking measurements from undamaged sides of an original screen, or measure width and height directly from window. Allow 3mm clearance for fitting and make sure window is square by checking that diagonals are equal. If screen is held in tracks, measure from inside of top track to outer top edge of bottom track so screen can be pushed into top track, then settle into shallower bottom track. Buy enough track for window or windows that need screening.
Screw flyscreen mitre box to a bench or saw stool to hold it steady.
Put frame, channel-side up, in mitre box. Use hacksaw to cut a 45° angle at 1 end of frame so channel will be on inside of mitre.
Measure length of frame piece from long point to long point (this will be the outside of a frame side) and cut a 45° angle in opposite direction. File cut metal to remove metal burrs. Cut other 3 sides of frame.
Insert corners and push frame tightly together. Check fit of frame in opening.
Put frame, with spline channels facing up, on a flat surface. Roll out mesh over top and align weave with frame. If it’s too large, cut so there is about 50mm overhanging all around. Use spline and spline roller to force mesh into grooves to hold mesh tight. This action will also tension mesh. If it goes wrong or wrinkles, simply pull out spline and do process again. If spline is too hard to press in, try placing it in hot water first to make it more pliable.
Use utility knife to trim excess mesh on outside of spline. Add catches and clips to screen or window as necessary and fit screen in place. Repeat process for other screens.