3Position the ADF’s mounting slots over the two mounting screws located at the back of the scanner. Slide the ADF forward slightly until the two holes in front of these slots are aligned with the screw holes at the back of the scanner.
Do not remove the protective foam block until you’ve finished tightening the ADF’s installation screws (see step 4.)
line up these holes with the screw holes on the scanner
screw holes on scanner 
position the ADF’s mounting slots over the two large screws on the scanner
Using Optional Equipment | Page 43 |