The elliptical trammel is a mechanism that uses two shuttles moving along perpendicular channels to trace an exact elliptical path. It works by inverting a double crank chain mechanism and fixing one link, so that when the two sliders move, any point on the central link traces out an ellipse. The semi-major and semi-minor axes of the ellipse are determined by the distances to the pivot points. This mechanism is used to precisely draw or cut ellipses.