As a divinatory line, nine at the fifth place of The Joyous reads within the hexagram's overall concern with progress and attainment, but advantage lies 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. It is also one of the two central lines of the hexagram, the place classical reading treats as the most balanced regardless of the line's own character. Its own text, that trusting in one who would do him injury, a perilous situation, though his place is the one correct and appropriate to him, is the particular fortune assigned to this one stage of the situation, not to the hexagram as a whole.
The fifth line corresponds by classical convention with the second line, and the two do not correspond here, since both lines share the same character. Read together with the trigram it belongs to, Dui in the upper position of the figure, the line marks the ruling stage of the hexagram, the place classical reading treats as its centre of authority, 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 fifth line of The Joyous turns Dui into Zhen while the other trigram, Dui, stays as it is, which yields The Joyous's changing partner, The Marrying Maiden (King Wen 54), the hexagram this line is recorded as transforming into.