If you’ve litigated a contract dispute in Maryland, you’ve likely referred to the “four corners” rule, which means the reviewing court interprets a contract based on the language within the document itself. If that language is unambiguous, the terms of the agreement control regardless of the parties’ subjective intent. A court considers “parol” or extrinsic evidence (evidence outside the contract itself) only if the terms of the contract are ambiguous. This foundational rule of contract interpretation appears in many cases, so a litigator could hardly be faulted for describing it this way. See, e.g., Walton v. Mariner Health of Maryland, Inc., 391 Md. 643, 660 (2006). But, as two recent Maryland Supreme Court opinions make clear, it’s not exactly right.