Final-Drill the screw attach holes in the W-1015-L Wing Tip to #28. Match-drill #40 the nutplate attach pattern into the W-1 015-L Wing Tip using a nutplate as a drill guide. Use a screw to position the nutplate in each hole, this will keep the nutplates aligned and will minimize puckering of the wing skins between attach the fasteners when the wingtip is secured to the wing. Machine countersink the nutplate attach holes for the head of an AN426AD3 rivet. Rivet the nutplates to the wing tip. Machine countersink the screw holes in the tip for the corresponding dimple in the wing skin.
This doesn't sound like much work, but with 42 holes per wing tip, that results in 246 holes drilled, 246 holes machine countersunk, and 168 rivets set. Not difficult, but tedious and time consuming.