I want to add screens to the wood-framed casement windows in my house, and while examining the existing frames, I found what appear to be connectors for screens (the oblong bit on the right in the photo). Only the windows that open have these. The fixed-pane windows don’t, which reinforces my assumption that these are for screens.
I’m planning to build custom screens myself, and I’d love to use these connectors if possible, to avoid drilling into the window frames. Does anybody know what these are called and what I would use to connect into them? The windows were made by Pella, if that helps.