C4 Charge Placement U.S. paratroopers place C4 explosive charge to a door before participating in urban breaching training as part of Exercise Rock Knight at Pocek Range in Postonja, Slovenia, July 20, 2017. Army photo by Paolo Bovo SHARE IMAGE: Download Image: Full Size (3.13 MB) Tags: Exercise Rock Knight, Soldiers, Army, training, European Command Photo By: Paolo Bovo VIRIN: 170720-A-JM436-107A.JPG Photo Gallery