Modern approaches to phonological knowledge encode that rate at which certain patterns hold directly into the grammar. This paper argues for a different approach to optionality/variability where the application of phonological knowledge is determined in the post-phonological phonetic production module. In this sense, phonological knowledge is never optional, but rather its inclusion when computing a phonetic exponent is optional. While the distinction is subtle, it accomplishes two things: first, it aligns with early generative views of grammatical knowledge as one of many factors that can be consulted during language use and second, it simplifies the phonological grammar by eliminating extra mechanisms such as diacritics and probabilities. This view is argued for based on a specific structure of the phonetics-phonology interface, the Blueprint Model of Production (Nelson & Heinz, in press), which formally situates phonological knowledge as one of many sources involved in phonetic production.