Hi Olga,

> The only way I see is to explode/trim the rail then I have
> a snap but I am loosing smoothness of the bottom part.

This would be the most normal way to force it to go exactly through the point you want, because by trimming the piece it forces you to get control points positioned exactly at the ends of the pieces.

You can maintain smoothness if you drag all the surrounding control points together at the same time instead of only the single ending ones.

You don't actually need to explode first before trimming, go like this:

Go to the right-side view and select this curve:



Run Edit/Trim, at the "Select cutting objects" prompt select the vertical curve as the cutting object, then Right-click in the viewport to finish picking cutting objects (or push the "Done" button, right-click is a shortcut for that), then at the "Select pieces to remove" prompt, right-click again to keep all pieces instead of discarding any.

That will split the curve into 2 pieces, here is just one of them selected:



Select both pieces and turn on control points by Edit/Show pts. Now select all 3 of the points along the bottom:




And click on the middle one and drag downward, and you will get an "int" snap (there is also a quad very nearby which is ok to grab as well) where the vertical line intersects the lower shape to get a good alignment:



The key thing for curve smoothness is that the 2nd point to the inside of a curve is important along with the ending point.

Those 2 points together define the tangent direction of the curve so if you move them together the tangent direction will not be disturbed.


There is actually another way to drag a point located on the curve to a different location - that is done by turning on control points for a curve, and then clicking and dragging on a point on that same curve. That will grab the point that you clicked on and move it to a new location and reposition the control points so that the curve goes through the new spot. But that tool does not work very well here because the "source point" is just the closest point to the curve from your mouse and is not snapped on to this specific "bottom most" point that you need in this case.

- Michael