GMC 2003 Sonoma Owner's Manual page 17

Jump Seat
If your vehicle has an
extended cab pickup, there
is a jump seat in the
rear area.
To fold the jump seat down, pull down
on
the pull tab
on the bottom of the seat until the seat
is in
place, then
move the seatback to a vertical position. To store the
seat, fold the seatback down on the cushion, then push
the entire seat up until it
is
flush with the trim panel.
Don't let the safety belts be damaged by the hinges or
the latches. Safety belts should be folded and stored
between the seat cushion and seatback.
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