The Black Leg Style is a martial-arts style that was created by Vinsmoke Sanji under training by Zeff. It is designed to free the use of one's hands and prevent them from being damaged during a battle, something that is disastrous to a chef like Sanji or Zeff. As a result, practitioners tend to drop into certain stances in which their upper-body portions are most relaxed, such as placing their hands inside their pockets or crossing their arms together across their chest, and only puts them into action whenever the event requires them to do certain maneuvers such as handstands, which aren't prohibited.