Edit NURBS > Intersect Surfaces

Creates curves on surface wherever two surfaces intersect.

Edit NURBS > Intersect Surfaces >

Create Curves for: First Surface causes only the first surface selected (the target surface) to receive a curve-on-surface.

Both Surfaces causes the target surface and the surface selected as the intersecting surface to both receive curves-on-surface. This is the default.

Note
If you select many surfaces, the last selected is the target surface. For example, if you select 10 surfaces, the first nine are intersected with the tenth.
Curve Type: Curve On Surface creates a curve-on-surface as the intersection curve. This is the default.

3D World creates a NURBS curve in 3D world space. The curve is not a curve-on-surface and cannot be used to trim the surface later on.

Note
Text cannot be intersected with a target surface because text is a collection of curves. You cannot intersect a surface and curve. To intersect text, you must create the text as trim surfaces.
Use Tolerance: The Use Tolerance options let you intersect within a specified tolerance of the default intersection. You can apply tolerance globally or locally.

Global tolerance causes Maya to use the Positional value in the Settings part of the Preferences window.

Local tolerance lets you enter a new value to override the value in the Preferences window.