As a divinatory line, nine at the third place of Revolution reads within the hexagram's overall concern with believed in only once it is accomplished, great progress and success, advantage in being firm and correct, so that any occasion for repentance disappears. The line occupies a place proper to its own nature in the classical doctrine that odd places favour a firm, yang line and even places favour a yielding, yin line. Its own text, that action taken now would be evil, and though firm and correct the position is perilous, but once the change has been debated three times over, he will be believed in, is the particular fortune assigned to this one stage of the situation, not to the hexagram as a whole.
The third line corresponds by classical convention with the sixth line, and the two correspond here, since one line is yin and the other yang. Read together with the trigram it belongs to, Li in the lower position of the figure, the line marks the hinge between the two trigrams, the last word the lower trigram gets before the upper trigram takes over, one stage in the six stage movement the hexagram traces from its first line to its last.
A change at this line, from yang to its opposite, is the mechanism the tradition uses to move from one hexagram to another. Flipping the third line of Revolution turns Li into Zhen while the other trigram, Dui, stays as it is, which yields Revolution's changing partner, Following (King Wen 17), the hexagram this line is recorded as transforming into.