Inverted dovetail cutter. By Artisan Makes. 3:46 video:
https://www.youtube.com/watch?v=YgwEwhm2cIU
Previously:
https://www.homemadetools.net/forum/...237#post184815
https://www.homemadetools.net/forum/...158#post180423
https://www.homemadetools.net/forum/...872#post179256
