Adjusting the head restraints of the rear seats mechanically
WARNING Risk of injury due to head restraints not being fitted or being adjusted incorrectly
If head restraints have not been installed or have not been adjusted correctly, there is an increased risk of injury in the head and neck area, e.g. in the event of an accident or when braking.
Always drive with the head restraints fitted.
Before driving off, make sure for every vehicle occupant that the centre of the head restraint supports the back of the head at about eye level.
Adjust the head restraint fore-and-aft position so that it is as close as possible to the back of your head.
To raise:
push release knob 
in the direction of the arrow and pull the head restraint up. To lower:
press release knob in the direction of the arrow and push the head restraint down. To set the centre head restraint in the first position:
pull the head restraint up.