Description: Autocrop and deskew are very useful features to have enabled on your scanner. Having them on means that slanted scans will be reoriented and black margins will be cut.
Scanner models: 5055, 5046
Process: Autocrop and deskew can only be enabled *only* when *both* scanner reference plates (see below) are set to black.
The following pictures might give you a better frame of reference for where these plates are located:
Finally, here's a video: