The protection of cyber-physical networks is a topic of increasing importance. The evolution of IT (cyber) systems that control and supervise the underlying physical system has grown over decades, whereas security has not become a concern until quite recently. Advanced persistent threats (APTs) have proven to be a difficult but significant challenge for practitioners. This work adopts a game-theoretic modeling of APTs and applies it to the (sub)problem of physical intrusion in an infrastructure. The gap between defining a good theoretical model and practically instantiating it is considered in particular. The model description serves to illustrate what is needed to put it into practice.