Dell 1600n Multifunction Mono Laser Printer - Manual (Page 51)

Printing to the Rear Output Slot (Face up)
Using the rear output slot, paper comes out of the multi-function printer face up.
Printing from the manual feeder to the rear output slot provides a straight paper path. Using the rear
output slot might improve the output quality with the following:
Envelopes
Labels
Small Custom-sized Paper
Card Stock
Transparencies
To use the rear output slot: