The name of a button (found on lenses without power retraction) that "releases" the lens from a given state. For example, to release the lens from its retracted state, the user holds this button while releasing the lens. Similarly, to release the lens from its extended state and retract it, the user holds this button and retracts the lens. In other words, this button is used to release the lens from its retracted state and return it from its extended state to its retracted state.