By a hand draftsman, a very light line drawn on the paper for a reference and not as part of the actual piece being drawn. In ClarisÊCAD, a line that goes all the way across the drawing to use as a reference. Construction lines do not print.
In Claris CAD, select the line tool and select the third method. Any line drawn with this method will cross the entire drawing. You can use the location bar to enter info about the line.