Mont. Code § 27-17-309
If the property taken is claimed by any person other than the defendant or the defendant's agent and the other person makes an affidavit of the person's title to the property or right of the possession of the property, stating the grounds of the right or title, and serves the affidavit upon the sheriff, the sheriff is not bound to keep the property or deliver it to the plaintiff unless the plaintiff, on demand of the plaintiff or the plaintiff's agent, indemnifies the sheriff against the claim by an undertaking by two sufficient sureties, accompanied by their affidavits that they are each worth double the value of the property, as specified in the affidavit of the plaintiff, over and above their debts and liabilities, exclusive of property exempt from execution, and are freeholders or householders in the county. A claim to the property by any person other than the defendant or the defendant's agent is not valid against the sheriff unless made as provided in this section.
§ 27-17-309, MCA