Mont. Code Ann. § 27-18-403

Real property or an interest in real property belonging to the defendant and held by any other person or standing on the records of the county in the name of any other person must be attached by filing with the county clerk a copy of the writ, together with a description of the property and a notice that the real property and any interest of the defendant in the real property, held by or standing in the name of the other person, naming the person, are attached. The county clerk shall index the attachment when filed in the names both of the defendant and of the person by whom the property is held or in whose name it stands on the record.