An arc ruler is a template, usually made ofMetal、WoodorPlasticIt is made up of many different segments of Euler's helix. It is used for...Hand-drawn illustrationsAndFashion designThey are used to draw smooth curves of different radii. Place the curves on the drawing material, and use a pencil, knife, or other tools to trace along the curves to obtain the desired results. They were developed by German mathematicians.Ludwig BöhmsterThe invention is also known as the Böhm–Bawerk curve set.