Dimpled the trailing edge of the wing skin. Countersunk the corresponding holes in the flap brace. Deburred the flap hinge. Finished the edge of the hinge with a Scotchbrite wheel. Blind-riveted the flap brace to the spar. Riveted the flap brace, flap hinge and wings skin together. Hung the flap and inserted flap hinge pins through the skin gap on top of the wing (the same way it'll have to be done once the flap is mounted on the airplane. This wasn't as easy as sliding a long hinge from the outboard side, but it was do-able -- the key is to lubricate the hinge pin first, and wear gloves to protect your hands from being pinched between the flap skin and wing skin.)