Proponents of present-day Science and Technology Studies (STS) tend to disregard classical phenomenological research by considering it incompatible with the performative turn in STS. The paper counters this tendency by exploring the case of so-called epistemic things and how this particular notion can be used to extend Heideggerian phenomenology. Heidegger is well-known for drawing a distinction between things that are ready-to-hand (i.e. handy) and things that are present-at-hand (i.e. unhandy). Although these two categories delineate many everyday objects, there are also instances where things cannot simply be considered as involving either handiness or unhandiness. One such example is that of drones used for detecting leakages in heat pipes. In being epistemic, these drones form part of a technical assemblage that can be used for uncovering and exploring suspected leakages – or knowledge objects – thus rendering the hidden visible.