The word 中规中矩 is formed by combining two parallel verb-object phrases, "中规" and "中矩", where "中" acts as a verb meaning "to meet" or "to conform to", and "规" and "矩" are nouns referring to the compass and carpenter's square, ancient tools for measuring circles and rectangles, respectively. The repetition of the structure emphasizes conformity to these instruments as metaphors for rules or standards, resulting in a fixed four-character idiom denoting strict adherence to norms.