The Sergeant at Arms is elected by the Senate and serves "from Congress to Congress until a successor is chosen." Law Enforcement and Security

As the Senate's chief law enforcement officer, the Sergeant at Arms is responsible for security in the Senate wing of the Capitol, the Senate office buildings, adjacent grounds, and for the security of Senators. Protocol

As the chief of protocol of the Senate, the Sergeant at Arms performs ceremonial functions that exist through custom and precedent. In carrying out these duties, the Sergeant at Arms greets and escorts the U.S. President, heads of states, and other official Senate guests while attending functions in the Capitol; leads Senators from the Senate side of the Capitol to the House chamber for joint sessions of Congress, to their places on the inaugural platform, and to any other place the Senate travels as a body; and assists in arrangements for inaugurations and the planning of funerals of Senators who die while in office. By custom, the Sergeant at Arms is custodian of the Senate gavel. The Sergeant at Arms is responsible for protocol surrounding the death of a Senator. Administration

As an administrative officer of the Senate, the Sergeant at Arms is responsible for specified services to Senators' offices, including the following:
acquiring home state office space, including mobile office space; purchasing office equipment and maintaining records of equipment use; operating computer support services; managing telecommunications services; establishing prices of items available for use in Senate offices; and administering orientation seminars for Senators, Senate officials, or members of the staffs of Senators or Senate officials and other similar meetings.
The Sergeant at Arms of the Senate is an officer of the Senate with protection, security, decorum, protocol, and administrative responsibilities. The Sergeant at Arms is elected by the membership of the Senate. As the Senate's chief law enforcement officer, the Sergeant at Arms is responsible for security in the Senate wing of the Capitol, the Senate office buildings, and on adjacent grounds.
As the chief of protocol of the Senate, the Sergeant at Arms performs ceremonial functions that fall within his jurisdiction through custom and precedent. In carrying out these duties, the Sergeant at Arms greets and escorts the U.S. President, heads of state, and other official Senate guests while attending functions in the Capitol; leads Senators from the Senate side of the Capitol to the House chamber for joint sessions of Congress, to their places on the inaugural platform, and to any other place the Senate goes as a body; and assists in arrangements for inaugurations and the planning of funerals of Senators who die while in office. By custom, the Sergeant at Arms is custodian of the Senate gavel.
As an administrative official of the Senate, the Sergeant at Arms is responsible for specified services to Senators' offices. In the administration of Senators' offices the Sergeant at Arms is responsible for securing home state office space, including mobile home state office space; purchasing office equipment; managing telecommunications services; establishing prices of items available for use in Senate offices; reimbursing Senators for items purchased through their offices; maintaining records of equipment used in offices; and administering orientation seminars, among others.