Laying out rivet patterns can take a lot of time, especially when the drawings specify distances from a leading edge or other reference mark, and the distances are not whole numbers. If you have to lay out a number of rivet holes on identical items, it is easy to make a measurement mistake if you go back to the drawing for each one. Fortunately, wing and tail ribs on a constant chord surface usually have the same pattern across the span, so you can use a little mass production to help you out.
I use some thin scrap aluminum cut into one-inch strips, with the edge made straight on a belt sander. Lay this against the full-size drawing and mark the rivet locations with a Sharpie. Be sure to include a “zero” point for an easy-to-find reference point, like the leading edge of the sheet. Label the template to make sure that if there is a difference between upper and lower surfaces, you don’t get things reversed-then move to your wing or tail skin and transfer the marks quickly and consistently.
The best thing about using a Sharpie on aluminum is that when you are finished, you can erase it all with some acetone and reuse the blank for your next marking project.
Lay a thin scrap of aluminum against a full-size drawing and mark the rivet locations with a Sharpie. Be sure to include a “zero” point for an easy-to-find reference point.