Extend

Used to extend or shorten a line or an end segment of a line string or multi-line.

You can access this tool from the following:

Setting	Description
Distance	If on, sets the distance. A negative distance shortens the line. A positive distance extends the line.
From End	(Applies for Distance off only) If on, the extension, or shortening, of the line is relative to the opposite point of the line. If off, the extension, or shortening, of the line is relative to the nearest endpoint to the selection point.

Key-in: TRIM EXTEND