2008 GMC Sierra 1500 Pickup Owner's Manual - Page 13

Rear Seats Rear Seat Operation (Split Bench) Folding Rear Seat On a vehicle with a second row 60/40 split seat either side of the rear seat may be folded for added cargo space. Notice: Folding a rear seat with the safety belts still fastened may cause damage to the seat or the safety belts. Always unbuckle the safety belts and return them to their normal stowed position before folding a rear seat. Make sure that nothing is on the seat. To fold the seat, slowly pull the seat cushion up. To return the seat to the normal seating position, slowly pull the seat cushion down. {CAUTION: A safety belt that is improperly routed, not properly attached, or twisted will not provide the protection needed in a crash. The person wearing the belt could be seriously injured. After raising the rear seatback, always check to be sure that the safety belts are properly routed and attached, and are not twisted. 1-9