The rudder stops rivet onto the aft end of the fuselage. They do what their name says: The stop the rudder's movement. We fabricated these out of angle aluminum, measured the drill holes, and trimmed one edge so that the bottom and aft sides would match up with the aft and bottom edges of the aft side skins. We then used these holes to match-drill holes into the fuselage skins and rear-most fuselage bulkhead flanges. These fit great.
We primed the two parts, then put them away for later riveting.
