Canon imagePRESS C800 Series Troubleshooting Manual page 182

Chapter 1
7) Return the saddle stitch staple cartridge for the Saddle Stitch Unit to its original position.
[Caution]
When the staple cartridge is put back, make sure that it is inserted far enough to match marks for the set position as indicated in the diagram.
[Reference]
Follow steps 2 to 7 and replace other staple case in the Saddle Stitch Unit.
8) Push the Saddle Stitch Unit (F-C4) all the way in and close the Front Cover.
- Push the Saddle Stitch Unit (F-C4) [1] all the way in. (Make sure that the Saddle Stitch Unit is inserted all the way in.)
- Close the Front Cover [2].
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