Elijah Bacchus, 36th Maintenance Squadron Precision Measurement Equipment Laboratory technician, calibrates the flatness of the base of a master level June 19, 2015, at Andersen Air Force Base, Guam. PMEL technicians calibrate anything from scales, digital voltmeters and generators to provide reliable equipment for the units they support. (U.S. Air Force photo by Airman 1st Class Arielle Vasquez/Released)