The Flap Brace W-721 was pneumatically riveted before the top skin was put on. This is a much easier way than putting in on after as per the instructions.
To dimple the Tailing Edge of the Rear Spar where it joins to the top skin was fiddly owing to the flange holes being up against the spar. The head of the squeezer was ground down otherwise it bends the carefully angled edge flange.
