Break Line
The Break Line command breaks the selected line at the currently selected point leaving one half of the line highlighted for easy deletion. To use this command, place the arrow over a line and press the Left button to select the point on the line. Type Crtl-X on the keyboard or choose Break Line from the Edit menu.
The F5 key breaks the line at the location of the arrow over the line, interpolates the grades and the inserts a point at the break points on each line segment.