Creates a reference plane tangent to a face.
The following face types are valid when constructing a tangent reference plane:
When constructing a tangent reference plane to a surface that is not a cylinder or cone, you must select a keypoint on the surface to which you want to attach the reference plane. The keypoint can be from an element that was used to construct the surface or from an element that was projected onto the surface. For example, you can project a line (A) onto a b-spline surface to create an curve (B) on the surface. You can then use a keypoint on the curve to define the tangency point for the reference plane (C).