Fill a large Pot with water. Bring to a rolling boil.
Place 1 un-opened can of sweet and condensed milk into the boiling pot of water.
Continue boiling for 1 1/2 hours making sure the water level stays above the can. Add more water if needed. Remove the can, open and let stand for 30 minutes or longer. Carmel sauce will thicken upon standing. Stir occasionally to help it thicken. Poor over ice cream, cake, or any deserts. Refrigerate.