Flex head socket wrench. By Mr Modify. 2:25 video:
https://www.youtube.com/watch?v=KrfkzYIEJ54
Previously:
https://www.homemadetools.net/forum/...480#post127809
https://www.homemadetools.net/forum/...623#post136394
https://www.homemadetools.net/forum/...692#post167157
https://www.homemadetools.net/forum/...576#post174158