Dell 3100cn Color Laser Printer - Manual (Page 63)

5. Remove the optional 250-sheet tray module or 500-sheet tray module.
6. Place the printer on top of the standard 250-sheet tray module.
7. Lock the standard 250-sheet tray module into place by removing the tray from the tray module and rotating the locking mechanism as shown in the
graphic.
8. Replace all trays.
Removing the Optional Memory Card