Autodesk AUTOCAD 2006, Command Reference Manual, Page: 1161 / 1490

The Specify End Tangent prompt specifies the tangency of the spline curve
at the last point.
last tangent point
If you specify tangency at both endpoints of the spline, you can enter a
point or use the Tangent and Perpendicular object snap modes to make the
spline tangent or perpendicular to existing objects. Press ENTER to calculate
default tangents.
Object
Converts 2D or 3D quadratic or cubic spline-fit polylines to equivalent splines
and (depending on the setting of the DELOBJ system variable) deletes the
polylines.
Select objects to convert to splines...
Select objects: Select 2D or 3D spline-fit polylines and press ENTER when you finish
SPLINEDIT
Edits a spline or spline-fit polyline
Modify II toolbar:
Modify menu: Object
➤
Spline
Shortcut menu: Select a spline to edit, right-click in the drawing area, and
choose Spline Edit.
Command line: splinedit
Select spline:
Enter an option [Fit Data/Close/Open/Move Vertex/Refine/Reverse/Undo]:
When you select a spline object or spline-fit polyline, grips appear at the
control points.
Change Dictionaries Dialog Box | 1137