Torus knot. Computer graphic of a knotted torus on a grid pattern. Knots are mathematical figures which are defined as enclosed spaces in three- dimensions based on a circle. Usually a torus is a three-dimensional ring shape. It is obtained by revolving a circle around a line which is in the plane of the circle but does not intersect the circle. The classical torus is 'doughnut' shaped. The knotted torus is obtained by drawing two- dimensional curves in the normal planes around a three-dimensional curve.