A vent stop is installed into a window/door to limit travel therein of a sash member, and being particularly adapted to permit ease of its installation, especially into a wooden door/window. The stop incorporates multiple retention means to inhibit the stop's removal, once properly installed. The retention means includes a wedge-shaped protrusion located at a distal end of the stop housing, which engages the wood of the window opening when pivotally installed therein, to secure a first end of the stop. The opposite end of the stop may be redundantly secured. A first means of securing the opposite end may comprise one or more arcuate flanges on housing side walls, flanges being adapted to unidirectional movement so as to permit its movement relative to the window opening during installation, but thereafter deterring counter-pivotal motion that would allow removal of the vent stop. A second means comprises a deformable spring clip.