Canon ScanFront 400 Instructions Manual page 178

4.
Remove any dirt from the roller using a cloth that has
been soaked in water and thoroughly wrung out.
5.
Install the cleaned retard roller by inserting the right
side first.
6.
Push the left side of the retard roller to secure it to the
scanner.
7.
Lower the document detection lever, and close the
roller cover.
178
Chapter 8 Maintenance