The traditional reading and writing sequence is generally from right to left, that is, reading and writing in batches horizontally from right to left, then reading and writing at the right door and reading and writing at the left door. Mainly because the ancients originated from a concept of courtesy.

Modern reading and writing order is out of habit, from left to right, that is, from left to right, reading and writing in batches horizontally. The upper part should also be posted on the left side of the entrance to the gate, and the lower part should be posted on the right side of the gate.

The characteristics of couplets:

1, with equal number of words: the number of words is not specified, but the number of words in the upper and lower parts is required to be the same. The number of words in the upper and lower couplets can be long or short, generally the shortest is four words, and the length can reach hundreds of words.

2. Same part of speech: same part of speech, same relative position. It is generally called "virtual to virtual, real to real", which means that nouns to nouns, verbs to verbs, adjectives to adjectives, quantifiers to quantifiers, adverbs to adverbs and related words must be in the same position.

3. Corresponding structure: the structure of the upper and lower links should be equivalent: that is, the phrases that make up the upper link are several words respectively, and the corresponding phrases of the lower link must also be several words respectively. And the structural types should be basically the same.

4. Flat words: Flat words should be harmonious and relative, especially the ending words of the upper and lower couplets should be staggered. The traditional habit is "flat and flat", that is, the ending of the upper couplet should be flat and the ending of the lower couplet should be flat.