Tech. Sgt Robert Holyoke (left), 28th Munitions Squadron support equipment technician, and Tech. Sgt Christopher Shields, 28th Munitions Squadron trailer maintenance NCO in charge, release the master cylinder as the last step of emptying brake fluid from a munitions trailer at Ellsworth Air Force Base, S.D., Feb. 7, 2013. The master cylinder is bled after each drum to ensure all brake lines have been cleared of air to guarantee the brakes work properly. (U.S. Air Force photo by Airman 1st Class Alystria Maurer/Released)