Dell C2660dn User Manual page 298

WARNING:
Never lay the waste toner box on its side as this may cause its malfunction or toner spills.
5 Remove the cleaning rod from inside the printer.
6 Insert the cleaning rod fully into one of the four holes until it clicks into the interior of the printer as illustrated
below, and then pull it out.
7 Repeat step 6 also on the other three holes. One time insertion is enough for each hole.
296
Maintaining Your Printer