Metal knurled knob retractable plungers are used in machining applications with limited space as positioners, loading pins, and indexing devices. Easy to grab metal knob allows quick actuation and locks out in fully retracted position to allow adjustment of the work piece. To lock, pull the metal knob back and turn 90°. To release, turn 90° once more and allow pin to engage in perforated holes. Locking patch available upon request.