def set_rigid_link(osi, r_node, c_node, rtype):
    """
    Create a multi-point constraint between nodes.

    Parameters
    ----------
    r_node: Node
        Master node
    c_node: Node
        Slave node
    rtype: str
        Either 'bar' or 'beam'

    Returns
    -------

    """
    op_type = 'rigidLink'
    parameters = [rtype, r_node.tag, c_node.tag]
    osi.to_process(op_type, parameters)
