With Shapes you can quickly apply predefined forms like circles, rectangles or spirals to an existing spline.
To create a new shape spline, click Create⇒Shape in the toolbar. A new spline will be created and the Shape Wizard
To immediately apply a shape to an existing spline, select the spline and click Shape in the toolbar to open the Shape Wizard
This wizard lets you select a shape template and set it's parameters
Select the shape template to use
Closes the wizard and makes the shape script permanent.
This closes the wizard, removing the shape script from the spline's GameObject