In this paper I consider the prospects for an epistemic norm which relates knowledge-how to showing in a way that parallels the knowledge norm of assertion. In the first part of the paper I show that this epistemic norm can be motivated by conversational evidence, and that it fits in with a plausible picture of the function of knowledge. In the second part of the paper I present a dilemma for this norm. If we understand showing in a broad sense as a general kind of skill teaching, then the norm faces counterexamples of teachers who know how to teach, but not to do. On the other hand, it we understand showing more narrowly as involving only teaching by doing the relevant activity, then the data which initially supported the norm can be explained away by more general connections between knowledge-how and intentional action.