To no ben (頭弁)
The term "To no ben" refers to a person who assumed the position of Benkan (Controller) concurrently with the position of Kurodo no to (Head Chamberlain) under Japanese government officials system. While the term "To no chujo" refers to a person who concurrently assumed the positions of Kurodo no to and Konoe no chujo (Middle Captain of the Inner Palace Guards), To no ben is normally understood as a person who concurrently assumed the positions of Kurodo no to and Chuben (Middle Controller) (of the Left and Right). Before the end of Heian period, however, some persons concurrently assumed the positions of Daiben (Major Controller) and Kurodo no to.
Summary
According to "Kantobisho," a book written by FUJIWARA no Toshinari, To no chujo was engaged in 'all matters at the Imperial palace' and To no ben was engaged in 'nationally important matters.'
The above book further stated that To no chujo was in charge of the role of close aides at the palace and To no ben was in charge of the communication between the Emperor and Daijokan (Grand Council of State) concerning political matters.
While persons of high-ranking court nobles were usually appointed to To no chujo, an ability for practical jobs was emphasized for To no ben. Accordingly, persons from middle-ranking court families that served for the Imperial court or sekke (line of regent and adviser) as the officer of practical job, such as the Kanjuji line and Hino family of the Northern House of the FUJIWARA clan and the Takamune school of Taira clan, were successively appointed to To no ben, and became common practice later. In the Muromachi period, To no ben was dubbed 'Tenjo Kanrei no to' (shogunal deputy at the palace) and played a role of the responsible person for various jobs at tenjo no ma (a chamber under the eaves on the south side of the Seiryo-den).