What is the view “window” (small round Plexiglas port at the upper rear corner of the access plate above the center hinge) on the rudder for? It allowed the rudder snubber/damper to be checked, and checking it was part of the pre-flight. How many plane captains or pilots actually walked back there straddling the vertical fin and hopped onto one of the elevators to check it? Few p/c’s and fewer pilots would be my guess. Gary Verver