Scan Tools > Surface and Curve Manipulation > Modifying Curves > Defining a Movement Plane for a Curve
  
Defining a Movement Plane for a Curve
When modifying a curve, you can select one of the following Movement Plane options on the Modify Curve dialog box:
Curve Plane—The movement plane is a plane that passes through the point’s tangency and curvature vectors.
Defined Plane—Select a datum plane to be the movement plane.
View Plane—The movement plane is the plane that passes through the point and is parallel to the screen.