As a divinatory line, nine at the third place of Obstruction reads within the hexagram's overall concern with advantage found in the southwest, and the contrary in the northeast, advantage in seeing the great man, and 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 going forward leads to difficulty, so he returns and remains still, 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, 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 Obstruction turns Gen into Kun while the other trigram, Kan, stays as it is, which yields Obstruction's changing partner, Holding Together (King Wen 8), the hexagram this line is recorded as transforming into.