The present invention is a positioning work stop for use with a machine tool for and having a signaling means that operates as a placement indicator effective for providing a signal if the work piece to be machined is in its proper position for machining or for signaling if the work piece has shifted out of position for machining. In a preferred embodiment of the invention the positioning work stop comprises a stop member having a stop surface, a switch element, a signaling means, and a power supply that are electrically coupled such that the signaling means activates when the work piece is in its proper position for manufacturing and for signaling if the work piece has shifted out of position for machining.