U.S. Army Sgt. Benjamin Acevado, 2nd Staff and Faculty Company Watercraft Engineer Certification Course student, tightens a locknut during an engine rebuild at Fort Eustis, Va., May 21, 2015. During the engine rebuild, students learn the steps of repairing and maintaining a diesel engine for any Army vessel. (U.S. Air Force photo by Staff Sgt. Natasha Stannard/Released)