U.S. Air Force Senior Airman Miles Roberts, reserve pararescueman, assists U.S. Marine Corps Cpl. Dan Peete, reconnaissance Marine, tie a knot designed to stay secure while rappelling during Exercise Angel Thunder 2015 high angle rescue training at Mount Lemmon, Ariz., June 1. During the training, U.S. Marines and U.S. Airmen practiced tying knots, anchoring ropes, rappelling down a cliffside unassisted, and returning to the initial elevation point. Exercise Angel Thunder is an Air Combat Command-sponsored personnel recovery exercise for combat air force, joint, allied and interagency participants. Roberts is assigned to the 304th Rescue Squadron at Portland Air National Guard Base, Ore., and Peete is assigned to Force Company, 1st Reconnaissance Battalion, 1st Marine Division at Camp Pendleton, Calif.