Custom of rubbing two sugar loaves together

Custom of rubbing two sugar loaves together: While the person is reading the espousal's to hold the sides of the espousal's napery on top of the bride and groom's heads while one of the bridesmaids, is rubbing two sugar loaves together . the very moment that espousal ceremony will be started , this white silk line napery must be held on top of the bride and groom's head till the end of the ceremony .