I do window screen repair Thousand Oaks and I know that a window screen can be very delicate if not treated right. The first thing you should know about screens is that to remove them, they first have to have screen tabs, if not you already are going to have problems. A screen frame tab is the rubber black square on the bottom of the frame that is there for you to hold on to.
If you are missing them, chances are that they probably broke off due to just being brittle. After a few years the tabs get brittle and crack off when pulled on, they just don’t last more than 7 to 12 years, depending on how much sun they get. Normally the screen mesh material needs to get rescreened every 7 to 12 years and that’s when the tabs get replace as well. Give me a call for a free estimate on all you screen needs.