Skin is personal and sensitive. As a result, design and placement of on-body physical interfaces need to be well thought out. One way of “getting the design right” is to quickly sketch a multitude of designs to be modified, adjusted and elaborated on. To date, on-body rapid prototyping methods do not afford these “quick-and-dirty” design processes. We propose using piezo-resistive kinesiology tape as a low-cost and versatile resource for sketching functional on-skin interfaces. Our method uses pre-treated kinesiology tape, which is made piezo-resistive through polymerization, and serves as touch, pressure and stretch sensor. We illustrate sketching techniques with both pre-treated and untreated tape for iterative design of on-skin interfaces. In addition, we contribute a set of sensor primitives that facilitate various input modalities for creating interactive sketches.