Staff Sgt. Derek Scrivener, 11th Security Support Squadron military working dog handler, does a practice sweep at the passenger terminal with MWD Lenox at Joint Base Andrews, Md., Dec. 8, 2016. The military working dog section supports approximately 210 distinguished visitor missions and more than 720 perimeter sweeps per year. (U.S. Air Force photo by Senior Airman Mariah Haddenham)