def _meeting_day_to_day(day):
    """
    Converts a string containing an integer number representing a day of the week
    into a string that contains the value for that day of the week

    Only does business weekdays

    DocTest

    >>> _meeting_day_to_day('-1')
    ''
    >>> _meeting_day_to_day('1')
    'M'
    >>> _meeting_day_to_day('2')
    'T'
    >>> _meeting_day_to_day('3')
    'W'
    >>> _meeting_day_to_day('4')
    'Th'
    >>> _meeting_day_to_day('5')
    'F'
    >>> _meeting_day_to_day('6')
    'Sat'
    >>> _meeting_day_to_day('7')
    ''

    :param day:
    :return:
    """
    if day == '1':
        return 'M'
    elif day == '2':
        return 'T'
    elif day == '3':
        return 'W'
    elif day == '4':
        return 'Th'
    elif day == '5':
        return 'F'
    elif day == '6':
        return 'Sat'
    return ''