Abstract: A casting unit in the sole of footwear is custom shaped to the foot of the user. The casting unit comprises a layer of a formable material, the upper surface of which is shaped to the contour of the foot by stepping down on the casting unit. This applies the weight of the user to the casting unit and displaces the formable material to form an impression which is an exact inverse of the foot and which therefore conforms with the contour of the foot.The edges of the layer are held in a fixed lateral position to cause the material to turn upward along the periphery of the foot. The resulting side and heel and toe containment provides, in combination with the foot sole impression, a positive foot-to-ground response and prevents rotation and slippage of the footwear from the foot.In one form of the invention the material is cured to a permanently molded form after it has been shaped to the contour of the wearer's foot.