Abstract: Disclosed in this specification is a cradle switch plug that is placed into a cradle of a dental instrument in a dental delivery unit to deactivate the instrument thereby allowing the instrument to remain at the ready without endangering or spraying the user and/or assistants and/or patients. In addition, when an instrument is removed from an air fitting a plug may be screwed into the air fitting. The plug prevents entry of debris into the ports thereof. The plug also enables proper seating of the air fitting within the cradle and, thus, actuation of the cradle switch.