Graphical user interfaces rely heavily on the tool metaphor. In most drawing systems, for example, functions are organized as they might be on a workbench; buttons associated with drawing modes for lines or rectangles are called linedrawing or rectangle-drawing tools; etc. Despite the similarities, however, there remain many di#erences between software tools and physical tools. This paper gives a concise account of tool use in general, and describes a drawing application, called HabilisDraw, that relies on a detailed correspondence to physical tool behavior