Thanks, everyone, for the kind words! Joshua, you're right, that extra wooden bit is a depth stop. It is a friction fit into the body and also locks into place with the wedge and arm for the fence. My next plow (as soon as I get a new set of irons) will be a "Yankee" plow that will be a copy of a Francis Nicholson plow from the 1740s. That one uses a threaded knob to lock the depth stop in place.