As a divinatory line, six at the fourth place of After Completion reads within the hexagram's overall concern with progress in small matters, advantage in being firm and correct, good fortune at the beginning but there may be disorder at the end. 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 a state of rags and worn out clothes kept ready, caution needed the entire day, 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, Kan 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 yin to its opposite, is the mechanism the tradition uses to move from one hexagram to another. Flipping the fourth line of After Completion turns Kan into Dui while the other trigram, Li, stays as it is, which yields After Completion's changing partner, Revolution (King Wen 49), the hexagram this line is recorded as transforming into.