2003 GMC 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. 1-10