This is another corner for window screen. The ones I found on MakerWorld were all for larger ‘hole' frames than were sold locally.

The aluminum frames sold at HD were listed as 7/16" on the box (as shown in one of the pics). 

So I designed my own corner in Tinkercad to fit the frame. For an exterior screen I printed it in PETG, while for an interior one I used PLA.

I just kept the whole corner solid rather than do cutouts or such - the minimal amount of plastic used means less to me than a large company printing thousands or millions of these.