Cut rind from watermelon (you should have about 4 1/2 pounds rind). Trim off the pink flesh and the green and pale green outer portions of the watermelon rind; discard those portions. Cut the rind into 1-inch squares or other shapes. Measure 9 cups rind.

Place the 9 cups rind in a large nonmetal bowl. In another large bowl, combine the 6 cups water and the pickling salt; pour over rind (add more water, if necessary, to cover). Cover bowl and allow to stand at room temperature overnight.

Pour the rind mixture into a colander set in sink. Rinse mixture under cold running water; drain well. Transfer rind to a 4-quart heavy pot. Add enough cold water to cover rind. Bring to boiling; reduce heat. Simmer, covered, for 20 to 25 minutes or until rind is tender; drain.

Meanwhile, for syrup, in a 6- to 8-quart stainless-steel, enamel, or nonstick heavy pot, combine sugar, vinegar, the 1 1/2 cups water, the stick cinnamon, and cloves. Bring to boiling, stirring until sugar dissolves; reduce heat. Simmer, uncovered, for 10 minutes. Strain mixture through a sieve, reserving liquids. Discard solids and return liquids to same pot.

Add watermelon rind to syrup in pot. Bring to boiling; reduce heat. Simmer, covered, for 25 to 30 minutes or until rind is translucent.

Pack hot rind and syrup into hot, sterilized half-pint canning jars, leaving a 1/2-inch headspace. Wipe jar rims; adjust lids.

Process filled jars in a boiling-water canner for 10 minutes (start timing when water returns to boiling). Remove jars from canner; cool on wire racks.