Samsung SL-M2070W-XAA - Manual (Page 49)

Media and tray
49 2. Menu Overview and Basic Setup
2 Load the original face up into the document feeder input tray. Make sure
that the bottom of the original stack matches the paper size marked on
the document input tray. 3 Adjust the document feeder width guides to the paper size.
Dust on the document feeder glass may cause black lines on the printout.
Always keep the glass clean (see "Cleaning the machine" on page 77).