Staff Sgt. James Foster, squad instructor, Drill Instructor School, MCRD San Diego, demonstrates sword manual to DI School students on the parade deck aboard Marine Corps Recruit Depot, San Diego. Foster and other seasoned drill instructors serve as mentors for Marines who come to MCRD San Diego to become drill instructors. - Staff Sgt. James Foster, squad instructor, Drill Instructor School, MCRD San Diego, demonstrates sword manual to DI School students on the parade deck aboard Marine Corps Recruit Depot, San Diego. Foster and other seasoned drill instructors serve as mentors for Marines who come to MCRD San Diego to become drill instructors.