Mont. Code Ann. § 25-15-101

When a judgment is recovered against one or more of several persons, jointly indebted upon an obligation, by proceeding as provided in Rule 4(s), M.R.Civ.P., those who were not originally served with the summons and did not appear to the action may be summoned to show cause why they should not be bound by the judgment in the same manner as though they had been originally served with the summons.