Most scanner covers feature standard hinges that lift only at an angle.
When scanning anything that isn't completely flat, the cover often becomes uneven and awkward. To address this problem, some scanners feature stationary posts instead of hinges. While the posts enable you to manually adjust height, the process is often clumsy and can result in the posts completely detaching from their postholes. In contrast, Canon scanners designed with the Z-Lid Expansion Top adjust for bulky items automatically. When the cover closes on top of a bulky item, such as a magazine or book, the hinge automatically lifts up to one inch high to create the space needed for the item while still keeping the cover flat.