Fujitsu ScanSnap S510M Operator's Manual page 54

3. Adjust the side guides to the document width.
Move the side guides so that they are touching the document edge. If there is clearance
between the document edge and the guide, the scanned images may be skewed.
HINT
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Document
If you use the stacker, it will be easy to gather scanned documents.
Use the stacker as described below.
1. Pull the stacker towards you.
Stacker
2. Use the indent and extend the stacker extension.
Indent
Side guide