The first step in the build up of the flap is to rivet all internal structure like the housing blocks and rib supports into the spar,
as the skin will cover these when attached.
This includes the rivets that attach the ribs that also form a tail on the inner of the spar. Now the built up frame is attached to the skin and jig assembly so the few hundred rivets the hold them together can be formed.
With the size of the flaps this is a two man job to get too both sides and form the rivets. Now the stringers that sit in between each rib are ready to go in, as well as the four small ‘L’ brackets that attach the stringers to the ribs.
Finally the majority of the structure has been attached to the skin, final steps will be to attach hinge and trailing edge.