def _configSpecial_OrthoOpts_xcentre(target, parser, shortArg, longArg,
    helpText):
    """Configures the ``xcentre`` option for the ``OrthoOpts`` class. """
    parser.add_argument(shortArg, longArg, metavar=('Y', 'Z'), type=float,
        nargs=2, help=helpText)
