def append_zeros_to_filtname(filtname):
    """Adds zeros to standardize the size of all filternames

    Parameters:
    filtname (str) - name of the filter file

    Returns:
    filtname (str) - name of the filter file, possibly now with zeroes inserted

    """
    while len(filtname) < 15:
        filtname = filtname[:6] + '0' + filtname[6:]
    return filtname