Trim dark green and pink from 2 lbs. watermelon rind. Cut in 1 inch cubes; measure 7 cups. Combine 1/4 cup pickling salt and 4 cups water; pour over rind (add water, if necessary, to cover). Let stand overnight. Drain; rinse rind. Cover with cold water. Cook until tender; drain. Combine 2 cups sugar, 1 cup white vinegar, 1 cup water, 1 tablespoon broken stick cinnamon, and 1 1/2 teaspoon whole cloves. Simmer 10 minutes; strain. Add drained rind and 1/2 lemon, thinly sliced. Simmer until rind is clear. Pack rind and syrup into hot half pint jars, leaving 1/2 inch headspace. Adjust lids. Process in boiling water bath 5 minutes (start counting time when water returns to boiling). Makes 5 half pints.