The Tip Ribs have a hinge pin installed on their outside face and a bent strip is installed between the rib and the spar for extra strength. The first task is to drill out and assemble the bent strips to the tip rib, starting with marking the location of the rivet holes.
I drilled pilot holes on the marks and then clamped the strip in place against the spar and the tip rib. First, I drilled the holes into the spar and then into the tip rib through the pre-drilled holes. 
To prepare the hinge pins I drew a line down the centre of each pin
and then pushed the pin through the back of the tip rib and turned it until the centre line showed up in the holes.
The hinge pins get riveted with A5 rivets so I drilled the holes through the pins, ribs and bent strip with the number 20 drill bit.