Sangen were always provided with some military instruments and weapons, and there was a rule that at least two kokushi (a provincial officer) of shitokan (four classifications of bureaucrats' ranks) should always be stationed to defend the seki.
三関には鼓吹軍器、すなわち兵器類が常備され、必ず複数の国司四等官が関を守護するため常駐する規定があった。