Placed bottom skin on fuselage and clamped in place. Traced stringers and bulkhead frames onto bottom skin. Removed bottom skin and placed on table and found center of stringers and frames and drew center line and laid out rivet line. Center punched and drilled each rivet hole with a 3/32 bit. Placed bottom skin on stringers and checked for alignment. Drilled rivet holes with #30 bit and clecoed every third hole as I drilled. Started on right bottom corner and worked forward using template that I had marked for the flutes on the bulkheads. Center punched and drilled rivet hole for 512 rivets and clecoed in place and repeated on left side.