I finished countersinking the spar webs then I worked on dimpling the main spar web, using the countersunk holes and a long rivet to do the dimpling. To make this jobs easier, I drilled a couple of holes on the bottom of the bucking bar so that I could place the rivet through the countersunk hole and have a solid backing for when I struck the head of the rivet using the bolt and hammer method. This worked well. I dimpled all of the holes for the rivets. I still need to dimple the holes for the machine screws. Onward!