 A related set of legal rules specify the core contractual text to be interpreted and what evidence determines its meaning. The “parol evidence rule” (“PER”) establishes a preference for writings over prior or contemporaneous oral agreements (UCC: §2-202). The rule, in its traditional statement, entails that where a writing exists, oral agreements (inferable from testimony) that are “extrinsic” to the “four corners of the document” do not become part of the contract. Some versions of the PER forbid the use of extrinsic evidence to “introduce an ambiguity” into a writing whose terms are otherwise clear and unambiguous. In addition, once the contours of a contractual text are set, principles of contract interpretation favor (to varying degrees in different jurisdictions) giving words meanings that are familiar to judges rather than meanings that are idiosyncratic to the parties. The interaction between the PER and the principles of interpretation entails a complication that runs through the legal practice of extracting meaning—namely that contracts themselves (especially written contracts) often seek to set their own boundaries and regulate their own interpretation, and the law both permits and resists such efforts.