https://www.acehardware.com/departments/hardware/window-and-screen-hardware/screen-framing/5164827
Prime-Line Gray Plastic 5/16 in. W X 3/4 in. L Screen Frame Corner 1 pk Mfr# PL7727 - Ace Hardware
Plastic screen frame corners designed to fit into square-cut ends of aluminum screen frame material to repair or construct new aluminum-framed screens....