Dell 2155cn/cdn Color Laser Printer - Manual (Page 632)

630 Maintaining Your Printer
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.
3 Load paper in the standard 250-sheet tray, and then insert the tray into the
printer and push until it stops.