Drew centerline on F-915 ribs. Assembled F-904 rear bulkhead to F-916 left and right ribs. Had to notch end of two ribs for snap bushing. Riveted ribs to the bulkhead. Bolted on bolts as directed and torqued. Marked nuts with torque seal. Messed up F-904H side doublers by countersinking in places I shouldn't have and will have to re-order.