As a divinatory line, nine at the third place of Development reads within the hexagram's overall concern with the marriage of a young lady, and the good fortune attending it, advantage in being firm and correct. 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 the geese advanced too far, onto the dry plains, a husband on expedition who does not return and a wife who conceives but does not nourish the child, evil, yet advantage in resisting plunderers, 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 do not correspond here, since both lines share the same character. Read together with the trigram it belongs to, Gen 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 Development turns Gen into Kun while the other trigram, Xun, stays as it is, which yields Development's changing partner, Contemplation (King Wen 20), the hexagram this line is recorded as transforming into.