Opus Dei's celibate members (numeraries, numerary assistants, and associates) practice three forms of corporal mortification that were traditionally used in religious orders and also by some laypeople in Catholic countries such as Spain. One of the more controversial forms of mortification is the use of a cilice, a small metal chain with inwardly pointing spikes that is worn around the upper thigh. The cilice's spikes cause pain and may leave small marks, but typically do not cause bleeding. Numeraries, associates, and numerary assistants are expected wear a cilice for two hours each day except feast days. Another mortification is to whip themselves with a small "discipline" (a corded rope whip) for a few minutes once a week while saying a prayer, as a participation in Jesus' scourging. (Escrivá had special whips for himself with metal tips on the end; these caused bleeding.) Additionally, female numeraries only are required to sleep on a board instead of a mattress; former female members have explained that Escrivá justified this rule by saying that since numerary women had to give up having children, they needed this mortification to keep them emotionally strong. Male numeraries are expected to sleep on the floor one night a week instead. Supernumeraries and associates, who do not live in Opus Dei centers (and hence share a bed or bedroom with family), are instead expected or encouraged to sleep without a pillow one night per week.