Hi Tudor, I'm sorry I don't really understand the question. Are you asking about the "autoplace" mode for Sweep? That is turned on if a sweep profile is outside of the rail curve's bounding box. When it's on the sweep profile will be moved to the rail and rotated to align with the rail's tangent and then swept along the rail path.

If the profile curve is inside the bounding box of the rail curve then it will not be moved and will be swept from it's current position.

- Michael