Jab saw from anchor bolt. By Handicraft. 4:29 video:
https://www.youtube.com/watch?v=Vt7PxGwkfRA
Previously:
https://www.homemadetools.net/forum/...462#post154814
https://www.homemadetools.net/forum/...250#post112988
https://www.homemadetools.net/forum/...911#post100290