Dell 2150cn/cdn Color Laser Printer - Manual (Page 388)

386 Maintaining Your Printer
Installing a Retard Roller in the Standard 250-Sheet Tray
1 Align the new retard roller with the groove on the axle.
2 Insert the retard roller into the axle until it snaps. The protrusions fit
completely into the slots and the roller hook reseats into the groove on the
axle.