U.S. Air Force Staff Sgt. David Perez, a trainer, instructs

U.S. Air Force Staff Sgt. David Perez, a trainer, instructs Airman 1st Class Justin Olsen, a patrolman, both with the 628th Security Forces Squadron, on grappling techniques during Personal Apprehension Restraint Techniques (PART) and Mechanical Advantage Control Hold (MACH) training at the combat arms building on Joint Base Charleston, S.C., June 5, 2012. The MACH and PART training is an annual requirement for the Airmen. (U.S. Air Force photo by Airman 1st Class George Goslin/Released)