Create Spline
Click to create control points to begin creating the spline. Once at least two points are defined, the spline will begin:
When the required control points have been added, right-click to continue. The handles for the spline will be displayed:
Move the handles of the spline to adjust the curve. You can press I to insert more anchor points, or CTRL click to remove them. The E key will extend the spline.
To finish the spline, either double-click as you digitise the last point or right click when complete.