This is a mock up (or as a cool teacher I used to work with would say:
'A first best effort') of a Jig to hold a Japanese blade.
Well of course I freehand sharpen - but when you get an old one....
That has a 23 degree bevel on it and you want to change it...
This just clamps into the honing guide.
Once you have enough flat you can stop using the jig of course.