Before the invention of paper, chops were used to seal written bamboo strips to prevent them being opened during delivery. One example of such a seal text dating from the Han dynasty reads: "I affix this seal because urgent business prevents me from coming in person; please open the enclosed letter which I now fasten with this seal."
現出土的漢印文字中有「某某印信，宜身至前，迫事毋問，願君自發，印信封完」字樣，意思是說：「我某人蓋這個印，本應親自前來，因有事沒空，邊有信，請你自己拆開看，現在封好了，並蓋上我的印」。