Ford F series Owner's Manual page 103

Check to see that the seat and seatback
are latched securely in position. Keep
floor area free of objects that would
prevent proper seat engagement. Never
attempt to adjust the seat while the
vehicle is in motion.
Relocking the seat after a tilt slide operation:
3. Push the seat backrest to its upright latched
position. Continue to push the seat rearward
to return it to its latched position. (This can
be done from inside the rear seat
compartment or from outside the vehicle.)
NOTE: The seat can no longer be moved
rearward when in its latched position.
Prior to operating the vehicle, check to ensure
that the seat assembly is locked by pushing or
pulling the seat forward or rearward. If seat
does not lock, repeat steps 2 and 3.
RWARNING
103