Cut corn from cobs and reserve for another use. Place cobs in water and bring to a boil. Cover and cook for 12-15 minutes. Remove cobs and strain liquid through cheesecloth. If neccessary, add water to make 3 cups. Place liquid in a saucepan and stir in sugar. Bring to a boil and cook until sugar is dissolved. Stir in pectin and cook 1 minute longer. Remove from heat, skim and spoon into sterilized jars. Seal and store. Makes 3 cups.