Canon Inner Finisher-L1 Service Manual page 21

3. The paper is fed toward the processing tray by the paddle. The return belt feeds the paper to the processing tray's stopper
and aligns paper in the feed direction.
4. The alignment plates are used to align paper in the width direction. (In the illustration below, paper is aligned with reference
to the central reference position.)
5. The operations described in steps 1 to 4 are repeated for each sheet to stack the sheets on the processing tray.
Paddle
Rear Alignment Plate
Front Alignment Plate
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2. Technical Explanation
Return Belt
Stopper