From Snopes.com: "Slipping a bar of soap into the bed as a leg cramp prevention has been advanced by a number of authorities, both medical and otherwise. Ann Landers mentioned the soap cure in her column on a number of occasions, with each airing prompting a load of letters from readers thanking her for this information because it worked wonders for them. 'They were thrilled and grateful to be liberated from those leg cramps,' said Ms. Landers. Yet skepticism aside, for those subject to noctural leg cramps, this bit of folk wisdom is clearly worth a try, in that the only potential downside is their having to share their beds with slivers of soap. (Well, that and having their spouses think them a bit loony.) As to what sort of product and where to place it in the bed, although some who pass along this bit of housewifely lore indicate specifics such as the soap's having to be unwrapped or not be a specific brand (Dial and Dove are often mentioned as bars to avoid), those who swear by the procedure have had success whether they used large bars or the small ones commonly found in hotel rooms, whether the cakes of soap were wrapped or unwrapped, and whether the afflicted leg was rested on top of the soap or not. As for which brand is best, other than Dial and Dove, they all seem to work about the same." It REALLY seems to work. I use an unwrapped bar of Ivory underneath the bottom sheet just below the knee area. It seems to work for aches and restless legs too. I don't have cramps.