A winding rod which has an elongated part disposed substantially perpendicularly to its longitudinal axis and being rotatable about the axis, an annular eyelet having a curved inner face partially surrounding the rotatable part that has an enlarged portion having an outer face curved complimentarily to the inner face within at least a section for cooperating with the outer face and being substantially coaxially disposed within the eyelet, the inner face being adapted to accommodate the outer face therein; the annular eyelet that has a circular or oval cross-section, curved suitably convex opposed inner faces at each side of the eyelet and tapering in the direction of each other, and a central aperture between the opposed inner faces.