As a divinatory line, nine at the fourth place of Before Completion reads within the hexagram's overall concern with progress and success, like a young fox that has almost crossed the stream when its tail gets wet, so there is no advantage in any direction yet. The line occupies a place that does not match 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 firm correctness brings good fortune and every occasion for regret disappears, as if in the excitement of using energy to subdue a troublesome region for three years, receiving reward from a great state, is the particular fortune assigned to this one stage of the situation, not to the hexagram as a whole.
The fourth line corresponds by classical convention with the first 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 upper position of the figure, the line marks the first word of the upper trigram, close enough to the ruling fifth line to be shaped by it, 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 fourth line of Before Completion turns Li into Gen while the other trigram, Kan, stays as it is, which yields Before Completion's changing partner, Youthful Folly (King Wen 4), the hexagram this line is recorded as transforming into.