Dell C3765dnf Color Laser Printer - Manual (Page 474)

472 Maintaining Your Printer
12 Reinsert the removed waste toner box.
CAUTION: If the waste toner box does not fit into place properly, make sure that the drum cartridge is fully inserted in
the previous step.
13 Turn the waste toner box lock lever 90-degrees clockwise to lock the waste toner box.
14 Close the right side cover.