The ability to use complex tools is arguably a defining human characteristic. The modal account of how this is achieved is that tools are ‘incorporated’ into the body schema—the putative internal representation of our bodies (Head & Holmes, 1911)—in order to control them as if they are a part of our body. Although compelling, we argue that this account remains essentially descriptive. By taking a sensorimotor approach, we hope to unpack the fundamental mechanisms underlying tool use more clearly. This involves first identifying canonical features of normal sensorimotor control of the hand—i.e. what does “controlled as if it is a body part” imply? We are then analysing the processes or steps needed to use tools in the same way. Then, finally, we are conducting empirical studies of tool use to see whether signatures of such processes are evident. We sometimes find that tool use rapidly resembles control of a body part, but we also find surprising ‘failures’, even for tools with similar mechanical properties and complexity. Our hope is that a better understanding of the factors driving these differences will ultimately help reveal fundamental principles of human tool use, which can in turn inform development of a wide range of emerging devices that, like tools, transform our movements, including surgical robots, VR systems, and powered prostheses.