Most aluminium Windows will have a provision for a fly screen called a recess. This usually is sufficient to contain the screen and allow removal, however in some cases it is not and to gain additional fixing you can use a springer or plunger pin. Plunger pins are fitted to the screens at the time of manufacture, they are small aluminium sections with a spring attached to that allows the ends to be retracted for easy removal. They can be fitted to just one side of the screen or both sides of the screen depending on the type of window. They are very useful for internal winder and casement style windows. To locate them into timber simply tap the back of the pin to create a mark then with a 5 mm drill create a hole. If needed this can be done to aluminium. Plunger pins can be selected as an accessory when purchasing your screen, they are then fitted during manufacture.