Completing the Horizontal Rule Properties dialog box
Use the Horizontal Rule Properties dialog box to change
horizontal rules in your draft.

Change any of the following options, and click OK:
Width indicates the length of the line.
To set a specific
line width for a horizontal rule, enter a number in the Width text
box, and then select Pixels. To set a line width that expands or
contracts depending on the width of a viewer’s browser window, enter
a number between 1 and 100 in the Width text box, and then select
Percent.
Height indicates the height of the line.
Use Outline Shading indicates that the line appears as an
outline, not a solid line.