Ford Mustang Owner's Manual page 112

Rear seat release straps
To raise the rear seatback:
1. Push the seatback upward until it locks in
place.
2. Make sure the seatback is firmly latched by
pushing forward and backward on it.
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.
Important Safety Belt Information
The use of safety belts helps to restrain you and
your passengers in case of a collision. In most
states and in Canada the law requires their use.
Safety belts provide best restraint when:
the seatback is upright
the occupant is sitting upright (not slouched)
the lap belt is snug and low on the hips
WARNING
111