After removing all of the clecos and labeling the inner ribs I proceeded to deburr the ribs. The outside was easy using my swivel deburring tool but the inside of the flanges was more difficult. I used some 220 grit Al oxide sandpaper on a popsicle stick to break the burrs off from the edges of the rivet holes. Next I used a scotchbrite pad so finish the ribs. With the ribs completed I proceeded to use a block of wood to hold the flap skin open to provide access to the inside. Again, I used the w220 grit Al oxide sandpaper on the popsicle stick to break the burrs off the edges of the rivet holes. With the skin deburred I reassemble the flap using clecos and started the riveting. Again, I left the flap such that it could be opened for inspection.