US Patent 7793421 Archway measuring device

Disclosed is a method and apparatus for drawing an instrument across a curve in a surface for constructing an arch. The apparatus comprises a base member having a pivot and a plurality of first indicators and a slidable member having a plurality of second indicators. The slidable member is slidably positionable on the base member. The method comprises pivotably securing the base member to a surface, selecting one of the plurality of first indicators corresponding to the chord height and selecting one of the plurality of second indicators representing the chord height and length of the arch to be scribed. The method further comprises aligning the first and second selected indicators, and rotating the apparatus about the pivot hole so as to draw across an instrument located at a distal end of the slidable member across an arc so as to define the arch.