Trimmed edges of reinforcement plates, R-605 horn, and ribs 404 and 403 using Scotchbirte wheel. Finish-drilled and deburred R-607PP & R-608PP reinforcement plates and spar. Primed plates and 3 platenuts using DuPont 215S primer. After laying skin into rudder jig and clecoing forward spar, clamped and drilled R-403 rib to spar. Dimpled last hole of each stiffener line next to trailing edge of rudder using pop-rivet dimpler.