This tool allows you to draw extension or witness lines from any line or flat side of an object in the drawing. To draw a witness line from a line or flat side of an object, select the Extension Line tool from the Dimension Tool palette. Place the cursor in the drawing area over a line or flat side of a rectangle or polygon. Press the mouse button.
Perpendicular snaps are available on request prior to clicking the mouse.
Drag in the direction that you want the witness line to go. As you 'pull' the line out, you will notice that there is a witness gap between the object and the witness line. Press the Shift key to eliminate the witness gap. Release the mouse button to end the line. The witness line will be placed in the drawing.