Senior Airman Benjamin Amirault, 28th Civil Engineer Squadron structures technician, inserts a piece of poly-metal into a large hydraulic shear machine for a crosswalk sign at Ellsworth Air Force Base, S.D., Aug. 15, 2013. As a less expensive, more durable alternative to aluminum, poly-metal is used in sign construction. (U.S. Air Force photo by Airman 1st Class Alystria Maurer/Released)