Deburred and polished the edges of the flap spars.
Marked the centerline on all of the rib flanges. These lines were used to center the ribs visually through the guide holes in the spars. Fitted the flap ribs to the spars and drilled the spar attachment holes to # 40. The first flap was the right one. I drilled the ribs with them oriented backwards. I misread the drawings and noticed the error when I saw "Rib Web" with an arrow that clarified the side that the web was on. When I re-drilled the holes, there didn't seem to be any problem with the new holes except on one rib. The hole may be too close together. I will put an extra rivet in any flange where there appears to be holes too close together.