The Customized DRF check box on the Feature Control Frame tab in the XactMeasure GD&T dialog box (Insert | Dimension | <dimension>) gives you the ability to create customized datum reference frames based on the Y14.5 2009 GD&T standard. When marked, lists appear inside square brackets, enabling you to select which degrees of freedom you would like to constrain. See "Creating a Customized Datum Reference Frame" for information.