exactly like planes.
The critical parts are
the blade support in back, the cap iron fit supporting the
un-beveled blade edge, and the distance between the edge and the
front sole – the opening of the mouth.
Check the blade support in the casting… this 15-dollar eBay
contemporary Stanley 151’s is fine… use Prussian Blue or soot
from a smoky lamp to find and flat needle files to take down any
Simply smoke or coat the blade, gently put it in place, and
tighten the slotted screw to make the marks.