Use Polygons > Cross Section to create one or more parallel cross
sections and store them in a separate object named Curves N.
Then you can:
Analyze the Curves object with Analysis > Analyze Curves.
Convert the Curves object to boundaries using .
Further process the Curves object with the Curve Menu, or save the object and use it with other applications.
Polygons > Section by Plane slices a polygon object into pieces.
It is not a cross sectioning tool per se, and does not create any new
objects.