Dell 1250c Color Laser Printer - Manual (Page 126)

124 Maintaining Your Printer
6 Insert the cleaning rod fully into the hole beside the arrow on the printer
until its tip reaches the interior of the printer as illustrated below, and then
pull it out.
7 Repeat the same procedure for the other three holes.
8 Return the cleaning rod to its original location.
9 Replace the black cartridge by adjusting it to the associated cartridge
holder, and then insert it firmly by pressing near the center of the label
until the cartridge clicks.