The male captives were normally chained together in pairs to save space; right leg to the next man's left leg — while the women and children may have had somewhat more room. The chains or hand and leg cuffs were known as bilboes, which were among the many tools of the slave trade, and which were always in short supply. Bilboes were mainly used on men, and they consisted of two iron shackles locked on a post and were usually fastened around the ankles of two men. At best, captives were fed beans, corn, yams, rice, and palm oil. Slaves were fed one meal a day with water, if at all. When food was scarce, slaveholders would get priority over the slaves. Sometimes captives were allowed to move around during the day, but many ships kept the shackles on throughout the arduous journey. Aboard certain French ships, slaves were brought on deck to periodically receive fresh air. While female slaves were typically permitted to be on deck more frequently, male slaves would be watched closely to prevent revolt when above deck.