Weighted lines are lines that are thicker than a "hairline." A hairline (the default) is the thinnest line that can be displayed or printed on a specific device. Cap options affect the ends of lines; join options affect the intersection of lines.
You can set the thickness of lines and the cap and join options of lines with Line Thickness 
in the format ribbon. If no objects are selected, you set a new default when you change the line thickness or cap and join options. Subsequent lines display with the selected width, height, and angle. In addition, you can change the weighted line options for a selected line.
For simple weighted lines, the width and height are the same, and the pen angle is set to zero degrees. You change only the width (thickness) of the line.
For a different effect, Designer can simulate a calligraphy pen (whose tip is typically taller than it is wide) and the way it might be used (at an angle in relation to the page). If you select Calligraphic lines, you can set the width, height, and angle of the "pen tip."
The Line Thickness menu displays previously used weighted lines so you can choose them directly from the menu.