2001 GMC Yukon Owner's Manual - Page 21

Head Restraints CAUTION: If a head restraint is not installed on the seatback or stored in the vehicle properly, it could be thrown about the vehicle in a crash or sudden maneuver. People in the vehicle could be injured. Remove the head restraints only when you need to fold the seat, and be sure that the head restraints are stored securely in the space provided on the folded up seat cushion. When the seat is returned to the passenger position, be sure the head restraints are installed properly. Slide the head restraint up or down so that the top of the restraint is closest to the top of your ears. This position reduces the chance of a neck injury in a crash. 1-8