3. (a) The Sergeant-at-Arms shall attend the House during its sittings and maintain order under the direction of the Speaker or other presiding officer. The Sergeant-at-Arms shall execute the commands of the House, and all processes issued by authority thereof, directed to the Sergeant-at-Arms by the Speaker.
(b) The symbol of the Office of the Sergeant-at-Arms shall be the mace, which shall be borne by the Sergeant-at-Arms while enforcing order on the floor.
http://clerk.house.gov/legislative/house-rules.pdf
http://history.house.gov/Collection/Listing/2006/2006-162-000/