Knots sit on a line during Angel Thunder 2015 high

Knots sit on a line during 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. Angel Thunder is an Air Combat Command-sponsored personnel recovery exercise for combat air force, joint, allied and interagency participants. (U.S. Air Force photo by Senior Airman Betty R. Chevalier/Released)