GMC 1996 Sierra Owner's Manual page 13

Head traints
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.
Seatback Latches
The front seatback of the base level bench seat folds
forward to let you access the rear of the cab. Your
seatback will move back and forth freely, unless you
come to a sudden stop. Then
it
will lock in place. If you
have a Crew Cab, your front seatback is designed not to
fold forward. Access to the rear of the cab is available
by using the rear doors.
The front seatback of all seats except the base level
bench seat folds forward
to
let you access the rear of the
cab. If you have a Crew Cab, your front seatback is
designed not to fold forward. Access to the rear of the
cab is available by using
the
rear doors.
To fold a seatback forward
on all seats except the base
level bench seat, pull this
lever forward and fold the
seatback forward.
To return the seatback to the upright position, just push
the seatback rearward until
it
latches. After returning the
seatback to its upright position, pull the seatback
forward to make sure it is locked.
The rear seatback of a rear bench seat without a center
armrest can be folded forward
to
let you reach
the
area behind
it.
Your seatback will move back and forth
freely, unless you come to a sudden stop. Then,
it will
lock into place.
The Crew Cab rear seatback with a center armrest folds
forward to let.you access the area behind
it.