The tools we choose to perform a given task affect not only the result of the task but also how it is conceived. An examination of tools, tasks, and interdisciplinary technology transfer suggests that new ways of thinking, rather than increased efficiency, are the primary means of technological advancement. The history of the relationship of the human body to architecture can be seen as a progression from embodiment to projection to a new paradigm of extension, or prosthesis. These ideas, together with surveys of bridge types and prosthetic technology, lead to the design of a pedestrian bridge linking two existing buildings. The bridge is conceived and designed using the tools of medical prosthetics and orthotics. Human and animal vertebrae suggest structural principles from which a light-weight, articulated bridge form is developed to satisfy the requisite conditions.