help with cutting the half of a brep intersection curve

[Thiru]

Hey folk..

Any one got an Idea, how to cut breps objects, that got thickness, so
it only goes the half.
I have seen others do the surface Half cut, by finding the midpoint of
the intersecting curve but on planar surface without thickness, But
how when the breps intersected got thickness, and without moving the
object?

Any way thx..