You need to measure width first W than height H should be W x H. Industry standard. This is How do you Measure for Retractable Screen Door .This is true for any style door or opening you want retractable screens for manual or motorized. Here we have shown different style doors. Retractable screens can be mounted Inside the frame or Surface all depends what will work best for each installation. and look. You can use screens for doors, french doors, sliding door, deck,pool or any other opening to keep the bugs out.