def select_resolution(structures, resolution_max):
    """
    Filter structures for structure with a resolution equal or lower than a given value.

    Parameters
    ----------
    structures : pandas.DataFrame
        Structures DataFrame from opencadd.databases.klifs module.
    resolution_max : int or float
        Maximum resolution value.

    Returns
    -------
    pandas.DataFrame
        Filtered DataFrame.
    """
    return structures[structures["structure.resolution"] <= resolution_max]