Chalked lined on upper rib caps. Drilled 1/8 inch holes on ribs 1 & 2 every 3 inches. Cleco'd nutplates in place to locate 3/32nd mounting holes. Drilled holes. Cleaned surfaces. Countersink 3/32nd rivet holes. Cleco'd nutplates into position, installed flush solid rivets, used rivet squeezer to compress rivets to secure nutplates.