Section

Create panel > Shapes > Splines > Object Type rollout > Section

Create menu > Shapes > Section

Tab panels > Shapes tab > Section Shape

This is a special type of object that generates other shapes based on a cross-sectional slice through mesh objects. The Section object appears as a bisected rectangle. You simply move and rotate it to slice through one or more mesh objects, and then click the Create Shape button to generate a shape based on the 2D intersection.

Here is a screengrab –

The white object is the section tool. The yellow line is the “cut” through the object. The rollout panel has a button named “Create Shape” that will activate when you select the section tool. When you create shape, it creates a whole new spline.