Dell 1815dn Multifunction Mono Laser Printer User Manual page 6

2. If you load paper that is longer than a standard (Letter or A4) size, such as Legal paper, press and unlatch the guide lock, and then slide the paper
length guide out completely to extend the paper tray to its full length.
3. Flex the sheets back and forth to loosen them, and then fan them out. Do not fold or crease the print media. Align the edges on a level surface.
4. Insert the paper stack into the paper tray with the side to be printed on, facing down.
5. Do not exceed the maximum stack height indicated by the paper limit marks on the both inside walls of the tray.
NOTE: Overloading the paper tray may cause paper jams.
6. Slide in the paper length guide until it lightly touches the end of the paper stack.
For paper smaller than Letter size, adjust the front paper length guide so that it lightly touches the paper stack.