Abstract: A ringed flexible leather brace has fastenings at each end portion. A rectangular hard leather including a stepped periphery and a longitudinal slender guide groove is integrally and vertically mounted on the face of the ringed brace and in the vicinity of one fastening to form a longitudinal slender and thin socket having a bottom opening. A first separable fastener is vertically attached on the rear side and at the corresponding portion of the socket. A bent plate spring having a straight upper portion, a straight lower portion and also an elastic belt including a second separable fastener is slidably inserted into the socket through the bottom opening to form a slidable engagement with the ringed brace.