A construction done using only a straightedge. The Poncelet-Steiner theorem proves that all constructions possible using a compass and straightedge are possible using a straightedge alone, as long as a fixed circle and its center, two intersecting circles without their centers, or three nonintersecting circles are drawn beforehand. For example, the centers of two intersecting circles can be found using a straightedge alone.

circle-circle intersection | geometric construction | Mascheroni construction | matchstick construction | neusis construction | Poncelet-Steiner theorem | straightedge