Together with shoinban, it was a kind of bodyguard in nature, so qualifications to become a Banshi (a samurai serving as a guard in the Edo period) were limited based on the Kakaku (family status) and post of his father.
書院番とともに親衛隊的性格を持つため、番士になる資格が家格や親の役職などで制限されていた。