How to Clean Lines on the Copier Glass

Does the issue happen only when using the Document Feeder?
Yes — with a clean dry lint free cloth, wipe the small slit glass to the left of main glass under the document feeder. Scan a document through the Doc Feeder and see if the line is gone.
Trick — scan a piece of blank paper through the doc feeder and place that paper next to the slit glass.  Where the line is on the paper is where the debris is on the glass.  Could be dust or ink, etc.
No — clean main charge and slit glass — see procedures for cleaning main charge