Splitting a curve at its virtual intersections with boundaries

The Extend curves check box (under More options of the Split Curve command) enables you to split curves also at their virtual intersections with boundaries (the ones you can get by extending the boundaries up to the curves to be split). If a boundary does not intersect the curve, nor does its extension, the curve to be split will be extended up to its intersection with the said boundary and split at the end point where the extension starts.

• When the check box is selected, the selected curves will be split also at their virtual intersections with the boundaries (i.e: the intersection points obtained by extending the splitting curves up to the curves to be split).
  If a boundary does not intersect the curve, nor does its extension, the curve to be split will be extended up to its intersection with the said boundary (which means that a new curve segment will be actually created) and contemporarily split at the end point where the extension starts.
  
  
   
• When the check box is not selected, the curves will be split only at their actual intersections with the boundaries.