Mont. Code Ann. § 7-3-4403

Each director shall conduct the affairs of the director's department in accordance with the rules made by the city manager and is responsible for the conduct of the officers and employees of that department, for the performance of its business, and for the custody and preservation of the books, records, papers, and property under its control. Subject to the supervision and control of the city manager in all matters, the director of each department shall manage the department.