Fujitsu ScanSnap N1800 Operator's Manual page 433

9. Insert the shaft back in the scanner.
Insert the top end of the shaft from above into the roller bushing located on the right
side as seen from the front, then set down the shaft until it is fixed in the scanner.
Then, adjust it slowly by setting it down.
10. Fix the bushing (located on the left side from the anterior view).
Rotate the left side bushing in the direction indicated by the arrow.
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Shaft
Bushing
Pick roller
Bushing
Shaft
Pick roller