The Ratcheting Expansion Screw (RES) was designed to eliminate patient deactivation of the appliance when removing the expansion key. The screw will lock into the advanced position eliminating the possibility of backing up. The screw also “clicks” when activated to give the parent and patient an audible signal the screw has been properly activated. The RES has been on the market for over 10 years and continues to grow in popularity. There have been several screws manufactured since the RES to try to mimic the ratcheting mechanism, but this is the original. It is important to use the specially designed safety key when activating the RES screw. The key is designated with a hole in the blue handle to differentiate it from standard safety keys. Regular activation keys will damage the holding clip.