U.S. Air Force Senior Airman Nathan Taylor, 1st Maintenance Squadron nondestructive inspection journeyman, operates a magnetic particle unit at Langley Air Force Base, Va., Nov. 3, 2014. A magnetic particle unit is used for detecting discontinuities in ferromagnetic parts. When magnetic particles are applied to aircraft parts, the poles attract particles and an indication of a discontinuity is formed. (U.S. Air Force photo by Staff Sgt. Antoinette Gibson/Released)