Canon imageRUNNER ADVANCE C5500 Series Service Manual page 441

3. If the height is not within the standard range, execute the following adjustments.
If the height is 19 cm or less: Turn the hexagon wrench counterclockwise.
NOTE:
Service Tool: Hexagon wrench (2.5 mm)
4. Check that the "height adjustment boss" does not contact with the Stream Reading Glass after adjustment.
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5. Adjustment