Staff Sgt. Carl Hunter, 28th Maintenance Group aerospace ground equipment craftsman, rebuilds flow control valves for a hydraulic aircraft jack at the AGE shop on Ellsworth Air Force Base, S.D., Sept. 28, 2011. The control valve limits the amount of hydraulic fluid leaving the jack’s hydraulic cylinder, thus regulating how quickly or slowly an aircraft is lowered after maintenance. (U.S. Air Force photo by Airman 1st Class Kate Thornton/Released)