Translations:Basic Sketcher Tutorial/17/en

Up to now when we have drawn lines and curves, the sketcher has added automatic constraints for us, those that keep the lines tied to the origin, and the O-arcs tied to the construction lines. But we haven't added other explicit constraints so the geometrical shapes can still be moved in many directions. Constraints are "rules" that tell us under which conditions a geometrical object can move and by how much. They are used to eliminate the degrees of freedom so that the sketch has a stable shape. If we eliminate all degrees of freedom, then the sketch is, and has a fixed shape, that is, its points cannot move at all. In general, it is a good idea to fully constrain sketches because this will result in stable models.