Embodiments of the present invention provide systems, methods, and computer storage media directed to an optical digital ruler. The optical digital ruler includes at least two optical sensors allowing physical movement and rotation of the optical digital ruler to facilitate positioning a template on a canvas or background. As such, a particular drawing stroke on the canvas or background can be drawn in alignment with a template irrespective of whether a path input by a user via a stylus aligns with the template. In some implementations, a drawing stroke is aligned with a template edge when the optical digital ruler has been activated despite the location of the path.