W12-02R and -02L Right and Left Hand Rear Spar Channel - Layed out locations for pilot holes for ribs. Layed out locations of holes for W13-04 doublers and W13-01R and W13-01L Attach plates. Drilled starter holes for doublers and attach plates. Used files and die grinder with scotch brite wheel to enlarge and polish the two holes on W12-02L.

Click on a link to view the video: