Staff Sgt. Michael Gwin, 28th Security Forces Squadron military working dog handler and his dog Rex stand at the Liberty Gate at Ellsworth Air Force Base, S.D., April 25, 2013. Gwin and Rex were posted at the gate to conduct vehicle inspections and ensure no contraband is brought onto base. (U.S. Air Force photo by Airman 1st Class Alystria Maurer/Released)