"Writing letters for others" was an old trade of bygone times; the practice is rare now. It is because that in ancient China, many ordinary people could not write. So when a family had a member travelling far away from home and no one at home could write a letter, they would usually turn to those who made a living by writing letters for help. The professional "letter-writer" would write down what the customer said to him and charged a few pennies for a letter.

In the past, when someone needed to appeal to the court for being wronged, claim a payment for debt, or file a lawsuit, he had to hand in a plaint form. The professional "letter-writers" could also help write the plaint form. In just a few lines the case could be explained clearly with forceful arguments, and the wrongs of the accuser may be corrected. In the Beijing opera Four Scholars Who Passed the Imperial Examination, Song Shijie, one of the heroes, is a professional letter writer.