An Expander Key is a tool used to turn the mechanism in some types of Palate Expanders. Turning the mechanism enlarges the Expander, which gently and gradually helps to enlarge the Palate. If you or your child have a Palate Expander, make sure to carefully follow your Orthodontist’s instructions on how to use the Expander Key. The above photo shows an Expander Key fit into the hole of the Palate Expander. The key should be moved in the direction of the arrow on the Palate Expander.