Epson Perfection V500 - Manual (Page 73)

To resize the marquee, position your cursor over the edge or corner of the marquee.
The pointer becomes a straight or angled double-arrow. Click and drag the edge or
corner to the desired size.
Note:
To restrict movement of the marquee to vertical or horizontal only, hold
down the Shift key as you move the marquee. To restrict sizing of the
marquee to the current proportions, hold down the Shift key as you resize
the marquee.
For best results and image exposure, make sure all sides of the marquee
are located inside the preview image. Do not include any of the area around
the preview image in the marquee.
To draw multiple marquees (up to 50; normal preview only), you can just draw them as
described in steps 1 through 3, or click the copy marquee icon to create additional
marquees of the same size. You can move and resize all the marquees as described in step
3. To delete a marquee, click inside it and click the delete marquee icon.