Staff Sgt. Van Black, academic instructor, Instructional Training Company, Support Battalion, shows recurits of Company D, 1st Recruit Training Battalion, how to treat a sunken chest wound aboard Marine Corps Recruit Depot San Diego, Oct. 23. During his demonstration Black discussed the moves he made and answered all questions from recruits. - Staff Sgt. Van Black, academic instructor, Instructional Training Company, Support Battalion, shows recurits of Company D, 1st Recruit Training Battalion, how to treat a sunken chest wound aboard Marine Corps Recruit Depot San Diego, Oct. 23. During his demonstration Black discussed the moves he made and answered all questions from recruits.