The last word of a couplet, if the last word is a conjunction, is a couplet. If the last word is flat and muddy, it is the bottom line. If the couplet is about time, then the old couplet is the upper couplet and the new couplet is the lower couplet.
There are many Spring Festival customs in our country, and posting Spring Festival couplets is one of them. The upper and lower couplets of Spring Festival couplets are the right hand and left hand facing the door, the upper part of the right hand and the lower part of the left hand, which is a way to distinguish us from ancient times to the present.