You can insert a horizontal rule across the page by typing four or more dashes. The number of dashes in a horizontal rule markup determines how thick it is, up to a limit of 10.
For more information on the possible markup, see HelpOnEditing.
<code> — (not a rule)
——————————————– (not thicker than 10) }}}
— (not a rule)
——————————————– (not thicker than 10)