Brother MFC-420CN - Manual (Page 27)

INTRODUCTION 1 - 7
1
Fan the pages well. Make sure you put the documents face
down, top edge first in the ADF until you feel them touch the
feed roller.
2
Adjust the paper guides to fit the width of your documents.
3
Unfold the ADF Document Output Support Flap.
DO NOT pull on the document while it is feeding.
To use the ADF, the scanner glass must be empty.
ADF Document
Output Support Flap