Airman Kaiulani Vila and Staff Sgt. Marco Castillo, 341st Missile Security Forces Squadron response force members, perform a perimeter check around a missile alert facility Aug. 28, 2017, near Belt, Mont. Perimeter checks along the fence line ensure the fence is secure and the warning signs around the area are visible. (U.S. Air Force photo/Airman 1st Class Daniel Brosam)