Given an identification between a cubic surface on "X" and the blow-up of formula_4 at 6 points in general position, the 27 lines on "X" can be viewed as: the 6 exceptional curves created by blowing up, the birational transforms of the 15 lines through pairs of the 6 points in formula_4, and the birational transforms of the 6 conics containing all but one of the 6 points.