a guide can provide proper registration of an object such as a hand above a scanner device for imaging . the guide can include windows or slits so that the scanner device can produce an image such as a finger or palm in a natural state rather than being pressed against , for example , a flat surface such as glass . thus , registration of a palm and / or a finger in the guide can be used to produce non - distorted high quality images of biometric patterns in their natural 3 - dimensional state .