2003 GMC Sierra 1500 Pickup Owner's Manual - Page 15

Rear Seats Rear Seat Operation (Extended Cab) Folding the Rear Seat 2. Fold the seat cushion upward until it latches with the seatback. 3. Push and pull on the seat to make sure the seat is secure. The extended cab's rear seat can also be folded open for more seating space. To use the seat do the following: 1. Push rearward on the seat cushion while pulling up on the release strap under the seat cushion. Pull the seat cushion downward until it latches. 2. After pulling the seat cushion down, pull up on it to make sure it is locked. 1-8