Mont. Code Ann. § 27-18-409

Investment securities, as defined in the Uniform Commercial Code, may be attached or levied upon only by seizure by the officer making the attachment or levy; provided that such a security which has been surrendered to the issuer may be attached or levied upon by leaving with the president or other head of the same or the secretary, cashier, or other managing agent thereof a copy of the writ and a notice stating that the security of the defendant is attached in pursuance of such writ. Stocks or shares or interest in stocks or shares of any corporation or company, other than such investment securities, may be attached either by seizure or by leaving with the president or other head of the same or the secretary, cashier, or other managing agent thereof a copy of the writ and a notice stating that the stock or interest of the defendant is attached in pursuance of such writ.