Canon LBP7210Cdn Manual page 399

IMPORTANT
Do not carry the printer with a cover or tray open.
Make sure that the front cover and multi-purpose tray are closed before carrying the printer.
NOTE
If the optional paper feeder is installed
Place the paper feeder on the new installation site before carrying the printer to the site.
For details on the procedure for installing the paper feeder, see
Put the printer unit down carefully at the new installation site.
CAUTION
Put the printer down slowly and carefully.
Be careful not to hurt your hands or fingers.
Insert the paper drawer into the printer.
Push it into the printer firmly.
"Paper Feeder".