http://esther.mathematik.uni-osnabrueck.de/tex/tex/online-help/ltx-158.html (Einblicke ins Internet, 10/1995)
\rule
\rule[raise-height]{width}{thickness}
The \rule command is used to produce horizontal lines. The arguments
are defined as follows.
- raise-height specifies how high to raise the rule (optional)
- width specifies the length of the rule (mandatory)
- thickness specifies the thickness of the rule (mandatory)