Completed left flap by riveting trailing edge and pop-riveting the bottom skin. Installed bushings in left flap hinge. Section 21 complete except for attaching flaps to wing. Began aileron assembly - dimpled all stiffeners and feft top and bottom aileron skings. Back riveted stiffeners and ribs to top and bottom skins. Assembled aileron, checked for bow, fabricated trailing edge piece, disassmebled then bent skin edges for overlap.