Toddlers rapidly develop hand and finger skills during their second year of life. They can now manipulate small objects with ease, turning the pages of books, building towers of blocks, and unzipping large zippers. Their newfound ability to coordinate their wrists, fingers, and palms allows them to turn rotating handles, unscrew jars and lids, use a cup with one hand, or unwrap paper from a piece of candy. Children at this age may be able to open doors, so special care is required to make sure they are supervised and in safe areas.
Shelov, S. P. (Editor-in-Chief). (2004.) Caring for Your Baby and Young Child: Birth to Age 5. The American Association of Pediatrics. Revised edition. New York: Bantam Books.