https://www.ucda.com/compass/
Objet d'art: Compass
Photo by July Velchev
A compass is a technical drawing instrument that can be used for inscribing circles or arcs. As dividers, it can also be used as a tool to step out distances, in particular, on maps. Compasses can be used for mathematics, drafting, navigation and other purposes.
Prior to computerization, compasses and other tools for manual drafting were often packaged as a set with interchangeable parts. By the mid-twentieth century, circle templates supplemented the use of compasses. Today those facilities are more often provided by computer-aided design programs, so the physical tools serve mainly a didactic purpose in teaching geometry, technical drawing, etc.
Compasses are usually made of metal or plastic, and consist of two “legs” connected by a hinge which can be adjusted to allow changing of the radius of the circle drawn. Typically one leg has a spike at its end for anchoring, and the other leg holds a drawing tool, such as a pencil, a short length of just pencil lead or sometimes a pen.
Source: wikipedia.org