A more thorough explanation:

The one-form-of-action rule is a principle in debtor-creditor law that states that when a debt is secured by real property, the creditor must foreclose on the collateral before proceeding against the debtor's unsecured assets. This is also known as the one-action rule.

For example, if a person owes money on a mortgage for their house, the lender must first foreclose on the house before trying to collect any other assets the person may have. This rule is meant to protect debtors from having all of their assets seized at once.

The one-form-of-action rule is also known as the one-book rule in the context of sentencing guidelines, which requires that only one version of the guidelines be used to calculate a defendant's sentence.

Another related principle is the one-court-of-justice doctrine, which holds that there is only one court in the state composed of several divisions, such as the supreme court, the courts of appeals, and district courts. Michigan has embodied this doctrine in its constitution.