As our contribution to this special issue, we examine how understandings of objects are talked and worked into being within concerted action. We will argue that formal procedure can serve as a resource in this regard. Procedures make relevant certain kinds of objects, objects that serve as its materials, tools, end-products, agents, etc. Our analysis traces all references to a particular object, the cystic artery, over the course of a surgery conducted at a teaching hospital. The arrangements of the operating theatre impose certain constraints on how the key participants, a surgeon in training, a faculty member and a medical student, were able to display and detect particular features of their material environment. Also, because of the surgery’s status as a ‘site of instruction,’ a special set of accountabilities came into play during its performance. Talk was frequently seen to do both instructional and instrumental work. The team members were called upon to interpret the visual field in congruent ways and, more specifically, to strike agreements as to what would serve as salient objects for the purposes of the work at hand. The identification of the cystic artery was called into question and its thingness had to be renegotiated. We draw on Garfinkel’s notion of ‘trust’ to describe the prospective/retrospective processes of referring to what comes to be the cystic-artery-for-the-purposes-of-this-surgery. We argue that procedure both determines and is determined by its objects.