Splines are similar to Beziér curves. You specify points sequentially, either with the mouse, snapping, or directly through X Y Z coordinate prompts. You can enter as many points as you wish. As you create each point, a curve is drawn approximating each point or through each point.
The options button in the dialog bar toggles the spline through four settings. The settings control whether the curve is an open or a closed interpolation or an open or closed spline. The four splines in the diagram all have the same defined points. They each use a different spline option though as shown below .
When you are done with the spline, press Create, or choose a new mode or tool and FeatureMILL automatically saves the spline curve. You don’t have to chain splines to make them function as curves for building profiles.