Head Restraint Bar
The head restraint bar forms the physical connection to the seat. The head restraint bar has ratchet grooves to allow for height adjustment.
To protect the pyrotechnic actuator connecting lead, there is a catch that prevents the head restraint being withdrawn beyond the maximum height position. This means that the head restraint can not be removed from the seat.
Similarly, head restraints with power adjustment can not be removed from the seat.