Sketcher > Modifying a Section > Modifying a Spline > To Add an Endpoint
  
To Add an Endpoint
1. Select the spline you want to modify.
2. Right-click in the Sketcher window and choose Modify from the shortcut menu. The Spline tab opens.
3. Press CTRL + ALT and then click a location in the graphics window. An end point is added to the nearest endpoint.