Canon imageRUNNER C3489 Reference Manual page 362

CAUTION
When closing the front cover of the finisher, be careful not to get your
fingers caught, as this may result in personal injury.
NOTE
If there are no staples ready for stapling after the cover is closed, the stapler unit
automatically performs a "dry" stapling operation to reposition the staples.
7
7-32
Finisher-Z1 (Optional)