Chapter 3 Datums 81 Angled Surface Datum feature symbol placed on edge view of surface or extension line from edge view Surface datum feature symbols must be clearly separated from dimension line arrowheads The Drawing The Meaning The Drawing The Meaning Example 3-3. Methods for placing datum feature symbols on datum feature surfaces. The datum feature symbol is placed on the edge view or on an extension line in the view where the surface appears as a line. The datum feature symbol can also be placed on a leader line directed to the surface. The leader line can be shown as a dashed line if the datum feature is not on the visible surface. Tangent plane: A plane that contacts the high points of the specified feature surface. When a surface is designated as a datum feature on a part, the datum feature symbol is placed on the edge view of the surface or on an extension line in the view where the surface appears as a line. Refer to Example 3-3. A leader line can also be used to connect the datum feature symbol to the view in some applications.