Deburr, degrease, prime and rivet wing ribs 4.
Rivet, except Rib 4 hinge bracket because this could need a little bend when mounting to the spar, doing the bend without being riveted to the rib is easier:
Orientation of flap bracket (right and left can be mixed easily):
Missing hole in stiffener plate, drilled the hole with a 4.9 mm drill:
Ribs 1 and 4 ready: