A central question in philosophical and sociological accounts of technology is how the agency of technologies should be conceived, that is, how to understand their constitutive roles in the actions performed by assemblages of humans and artifacts. To address this question, I build on the suggestion that a helpful perspective can be gained by amalgamating "actor-network theory" and "postphenomenological" accounts. The idea is that only a combined account can confront both the nuances of human experiential relationships with technology on which postphenomenology specializes, and also the chains of interactions between numerous technologies and humans that actor-network theory can address. To perform this amalgamation, however, several technical adjustments to these theories are required. The central change I develop here is to the postphenomenological notion of "multistability," i.e., the claim that a technology can be used for multiple purposes through different contexts. I expand the postphenomenological framework through the development of a method called "variational cross-examination," which involves critically contrasting the various stabilities of a multistable technology for the purpose of exploring how a particular stability has come to dominate. As a guiding example, I explore the case of the everyday public bench. The agency of this "mundane artifact," as actor-network theorist Bruno Latour would call it, cannot be accounted for by either postphenomenology or actor-network theory alone.