Metaphoric understandings emerge when conceptual mappings link elements of one domain with elements of another. Cross-domain mappings seem powerful and creative, but even mundane meanings involve mappings that link elements with one another. Instructional interactions bring the process of conceptual mapping into the open as one person strives to shape the understanding of another. Using data from a study of time-telling instruction, this chapter describes two important functions of gestures during instruction: (1) guiding mappings that link conceptual models with structures in the environment, and (2) adding image-schematic structure to the conceptualization. Both help form the understanding needed to perform successfully. These critical functions of gesture are apparent only when discourse is treated as multimodal and contextual – as involving the interrelation of talk, gesture, and action with the setting and purpose of activity.