|Countersinked the reinforcement spar and dimpled rear spar
After walking back and forth multiple times looking at the plans to make damn sure I was working on the right side of each spar, I started countersinking and dimpling the spars. I dimpled the main rear spar first. Then I started countersinking the reinforcement spar, making sure that the dimpled main spar went all the way down into the reinforcement spar countersink. I had a single flat head rivet that used to check the depth of each countersink.