The latest ANSI drafting standards allow a datum symbol to be attached directly to a dimension line (the one with the arrows) in order to show the feature of size as a datum. When trying to attach a datum to a dimension line, the datum orients the one end of the dimension line or the other and parallel instead of perpendicular to it. This actually gives the appearance of the datum being attached to the extension line therefore representing the edge of the part as being the datum. The entire point of using GD&T is to show design intent and one is different than the other. How does one show design intent using a feature of size as a datum?