Dell 3100cn Owner's Manual page 13

Squeeze the length guide and slide it to the edge of the tray.
3.
Before loading the print media, flex the sheets back and forth, and then fan them. Straighten
4.
the edges of the stack on a level surface.
Place the print media into the tray with the recommended print side face up.
5.
NOTE:
Do not exceed the maximum fill line in the tray. Overfilling the tray may cause paper jams.
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