How do you fit a curve between two points?

I know that it is simple but what command can I use to make a curved cross section line fit in between two other enpoints of other curves that I am using as rails? The cross section is a different size than the opening at the rails and I want the cross section curve to be scaled and reoriented to meet at the rails’ two endpoints. Does that make sense?

Orient if the ends of the cross-section curve and the target ends of the rails lie on a plane parallel to the CPlane. Set Scale=1D or Scale=3D as desired.

Orient3Pt for more general situations.

thank you!