U.S. Marine Gunnery Sgt. Robert Turek demonstrates locking out while rappelling in the hangar bay of the USS Essex (LHD 2) in the East China Sea, June 2, 2015. Turek is a member of the 15th Marine Expeditionary Unit’s Maritime Raid Force. Locking out allows the Marines to stop descending in case they need to fix their gear or their landing area becomes unsafe. (U.S. Marine Corps photo by Cpl. Elize McKelvey/Released)