The techniques used to make preoperative markings before soft tissue reconstruction have remained relatively unchanged since the earliest years of plastic surgery. Using skin-marking pens, many surgeons continue to draw markings freehand as "best estimates" before their first incisions. Although efficient for the experienced surgeon, this strategy may prove challenging for residents and trainees striving to learn and maintain consistency while replicating the intricate geometries of flap markings. To address this need, Operating Room Stencil was developed as a novel tool for digitally planning flap markings that may then be projected onto contoured surfaces such as the human body. As a cost-free mobile application, Operating Room Stencil is widely accessible to the medical community and offers educational captions for a majority of the flaps featured in its database. Users can plot relaxed skin tension lines onto uploaded facial images, thus enabling surgeons to orient surgical markings in a way that optimizes scar formation and reduces wound contraction. Although originally intended to appeal to trainees as a reliable way to learn about flaps and practice their technique, Operating Room Stencil may prove useful even among more experienced surgeons striving to further perfect their visualization and execution of flap markings.