Disclosed is a plastic clamping ridged strap which can clampingly hold an object such as an electric wire, onto a plate in cooperation with associated apertures in the plate. The clamping strap according to this invention is composed of an elongated plastic band molded to have a plurality of tall and short ridges arranged alternately with each other in such a way that each tall ridge is nearer to one adjacent short ridge than to the other. The ridged strap can pass the associated aperture of the plate only in one direction by allowing the tall ridges to yieldingly bend down when caught by the opening edge of the associated aperture. The ridged strap, however, cannot pass the associated aperture in the other direction because the short ridge will prevent the tall ridge from bending to a level low enough to allow the ridged strap to pass the aperture.