These two tool create curves, one by finding the intersection of two solid objects, and the other by projecting a 2D object onto a 3D solid.

Intersection

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Creates curves along the intersection of two solids (not surfaces). This tool does not work with surface objects.
Select the first and second solid objects. This example shows a sphere and a hemisphere.

The intersection curves are created.

Projection

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Projects a 2D curve onto a solid (not surface) face. The 2D curve can be open or closed.

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