Third and Fourth rib from the tip RH and LH. Plot of assembly and flat patterns. Paste to aluminum (just bought 1 qt of rubber cement) and cut, line in middle is bend line. Holes are in the top pieces of the assembly for drill through at assembly after mounted in the jig. The plotter is within .01 and on 100% rag Vellum it is very stable. The pen plotter is better than my printer, but for small parts the printer would work ok. It is easier to keep the parts straight if I plot them all for any rib on one sheet. The only problem I have had is it is best to wait 12 hr for the glue to dry, as the vellum does not allow air through much.