Paiwen 牌文 were express orders. The original meaning of the word pai 牌 was a kind of permit or certificate used by messengers, envoys or commissioners or attached to objects sent for a special mission, mainly official documents and letters. The certificate proved the authenticity of the mission and allowed for a set of fresh horses, provision and accommodation in courier stations.
During the Song period 宋 (960-1279), the words paiwen, xinpai 信牌, chuanxinpai 傳信牌, xipai 檄牌 or dipai 遞牌 were used for such certificates. They were made of wood. Depending on the purpose, the Southern Song 南宋 (1127-1279) discerned between "golden" certificates (jinzi pai 金字牌) written with lacquer in cinnabar colour on yellow ground (or with cinnabar lacquer mixed with gold powder), "green" certificates (qingzipai 青字牌; bluegreen characters on dark yellow ground), and red certificates (hongzipai 紅字牌; red characters on black ground). In addition to the paiwen, which was written on wooden tablets, couriers carried with them an embossed silver token (yinpai 銀牌).
The Yuan dynasty 元 (1279-1368) exchanged the wooden certificate slips by such written on paper (xinpai), used if regional government sent messages to local administrators. The documents carried the date of mission and a document number (zihao 字號) glued directly on the document to be transmitted. During the Ming period 明 (1368-1644), the size of the certificate paper was enlarged and printed according to a defined style, with a width of about 40 cm, and somewhat more in height. The message was directly written on this paper in the right half of the paiwen paper. The message was inscribed with the characters xinpai 信牌 and in the left upper corner with the name and office of the sender, the date, his seal (actually the left half of the seal, while the right half was on the archived copy of the sender), the number of the document.
While the Ming dynasty used this kind of message mainly for military purposes, the Qing dynasty 清 (1644-1911) opened it to the civilian realm, mainly on the local level in top-down direction, but also when central-government institutions send massages to subordinated institutions. Examples are orders sent by a governor-general (zongdu 總督) or provincial governor (xunfu 巡撫) to the provincial administration or circuit intendants (daotai 道台), superior prefectures (fu 府) writing to second-class prefectures (zhou 州) or districts (xian 縣), or prefects (zhizhou 知州) and district magistrates (zhixian 知縣) sending orders to their underlings. In the military realm, they were used if a provincial military commander (tidu 提督) issued an order to a regional vice commander (fujiang 副將) or a regional commander (zongbing 總兵) such to an assistant regional commander (canjiang 參將). Apart from the name xinpai, the terms xianpai 憲牌, xingpai 行牌, paipiao 牌票, paixi 牌檄 and paiwen were used for these rather short documents. The beginning and end of paiwen documents, as well as important phrases were usually marked with red dots or annotations (biaozhu 標硃, biaoji 標記). An answer to paiwen orders was not expected.
Other types of documents had special purposes, like urgent military orders (huopai 火牌) issued by the Ministry of War (bingbu 兵部), military tokens (bingpai 兵牌), protective tokens (hupai 護牌) to identify persons, transmission tokens (chuanpai 傳牌) or "achievement tokens" (gongpai 功牌) similar to military decorations, allowing the token’s bearer special treatment.