Canon imageRUNNER C3489 Reference Manual page 369

5
Insert the new staple cartridge.
NOTE
Only one front and rear staple cartridge can be inserted at a time.
6
Pull the stapler unit of the saddle stitcher unit towards you,
and then push it down into its original position.
7
Gently push the saddle stitcher unit back into its original
position.
Finisher-Y1/Saddle Finisher-Y2/Puncher Unit-M1 (Optional)
7
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