GMC 1999 Sierra 1500 Pickup Owner's Manual page 20

Seats & Safety Belts
If you have a Four Door Model, your front seatback is designed not to fold
forward. Access to the rear of the cab is available by using the rear doors.
There's one time the seatback may not fold without some help from you.
That's if your vehicle is parked going down a fairly steep hill. If this happens,
push the seatback toward the rear as you lift this latch. Then the seatback
will fold forward. The latch must be down for the seat to work properly.
Seatback Latches (Bench Seat With Armrest)
K2547
The front seatback folds forward to let you access the rear of the cab.
If you have a Four Door Model, 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, pull this lever up 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.
1
CAUTION
If
the seatback isn't locked,
it
could move forward in a sudden stop
\
or crash. That could cause injury to the person sitting there. Always
press rearward on the seatback
to
be sure
1
i t
is locked.
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