Without units, there are no boundaries; and without boundaries, there are no units. Traditional linguistics takes units such as sentences and intonation phrases for granted, treating them as static. Interactional linguistics has reconfigured many of these units, treating them as emergent, focusing on their evolution in time, and how they implement social actions. A productive line of research of interactional linguistics has been this tension between conventional linguistic units and units of (and for) interaction (Reed and Beatrice 2013; Ogden and Walker 2013). The cesura approach (Barth-Weingarten 2016) focuses on the constitution of phonetic-prosodic discontinuities, which give rise to boundaries, "cesuras", which it treats as a continuum from "no cesura" through "candidate cesuras" of various strengths, to "full cesuras". However, there are also elements of spoken interaction whose unit-hood is not obvious at all levels of description; and it is a subset of these that form the focus of this article. We illustrate this with extracts of multimodal talk where two interactants taste and assess unfamiliar food and produce the token "mm". We show how the alignment (and non-alignment) of boundaries of sequential, prosodic, gestural, lexical, and syntactic units can be a semiotic resource. Data are obtained from Chilean Spanish.