1. Remove the middle left cover. (Middle Left Cover)
  2. Remove the screw (a)(M3x8).
  3. Pull the rib (b) toward the machine front side and release the center hook (c).
  4. Release the hook (c) using a flat-blade screwdriver.
  5. Detach the lower left cover (d).

When attaching the lower left cover (a), insert two bosses (b) at the machine front side into the holes and apply the center hook (c). Then, attach it with the screw.
Check if the hook at the center is surely fastened.