Today was a nail biter. I marked, checked, re-checked and re-checked the cut-out for the wing locker in the the top wing skin. This was not where I wanted a big cut goof.Using the Olfa knife, (which I didn't have much faith in), the cuts went perfect... then it was time for a JD.Sprayed Zinc C on locker "L's" as required...after dry I riveted locker door- complete.