Flap drive pin install 4.

There's a 12 foot straight edge taped to top of the wing that is parallel with the spar.
Situated over the top of the flap there's a 4 foot straight edge.
The steel straight edge you see in this pict is resting on the 4 foot straight edge and can be moved inboard or outboard to allow for different length drill bits. It is used to sight the drill bit parallel to the spar.
Y10-12-01