Oki OKIFAX 5400 Maintenance Manual page 123

a)Insert the tip of a cutter or Nipper between the mold of Rear Cover and cut out it.
Note: Be careful not to rotate the cutter or Nipper, since this can cause scratching on the Rear Cover.
b)Grasp the mold of Rear Cover, and rotate it up and down until you can able to easily remove it.
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