Airman 1st Class Chun Liu, 28th Maintenance Squadron aerospace ground equipment technician, secures a lid to an oil cart during scheduled maintenance at Ellsworth Air Force Base, S.D., April 18, 2012. A proper seal is necessary to ensure the oil cart is secure while operating inside the B-1 bomber. (U.S. Air Force photo by Airman 1st Class Alystria Maurer/Released)