AirBike rudder hinge clarification

To all those that responded to my previous post looking for AirBike
plan, thanks. I now have a set for the two-seater.

This post goes out to all those that have a set of plans and/or have
built one.

While studying the plans, I notice on the drawing for the vertical
stab that the lower rudder hinge is drawn as I would expect a hinge to
be: a couple of interleaving fingers joined by a pin. However, I'm
unable to make sense out of the upper hinge. Is this detail a mistake
or is there some special hinge design I'm not getting?

Thanks