Plustek OpticBook A300 User Manual page 26

Always Lock:
It holds the scanning head in place during transportation and traveling. The
scanner will be kept in disabled status. To lock the scanner, slide the locking
switch on the scanner's underside toward the power LED of the scanner until it
snaps into place.
Warning
When you need to move the scanner, do lock
the scanner to ensure accurate and problem-
free use of your scanner.
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