At Balenciaga, the models' legs were caged in futuristic footwear made of metal plates laced up to the knees with braids. At Yves Saint Laurent, the soles of Mr. Pilati's needle-thin stilettos were replaced by a thin metal rod that connected the heel to the toe, leaving the most sensitive — some would say erotic — underbelly of the foot vulnerably exposed. The models looked as if they were walking a tightrope, and the audience was made to feel alternately fascinated and terrified.