Top and bottom
Chinese idiom, Pinyin is Gu à NSH à NGL à Xi à. It comes from the biographies of scholars in historical records.
explain
The metaphor is clear from top to bottom.
source
According to the biographies of scholars in historical records: "although the crown is worn, it must be added to the head; although the shoes are new, it must be about the feet. It's up and down. "
Top and bottom