"Kebiki" Cutting Gauge. I made it with hand tools; the cutter is a piece of hacksaw blade I snapped to size and shaped on the belt grinder. This thing is way beefier compared to the others I see on the internet--I made it based on a drawing in a book by Toshio Odate with little sense of scale. I vaguely recall seeing a big one like this in a video. I didn't put the maker mark on it because it doesn't meet ergonomic specs, but it's very functional regardless.
Have to grind off the top of the blade and back it off a little, it's deeper than needed-