Abstract: An apparatus for positively locking a ball screw in a lift position is described. The apparatus includes defined tooth disc and pawl housings, which interconnect to facilitate interoperation of locking components. A tooth disc is secured to the ball screw and actuators associated with each pawl can exert a downward force on each pawl, in order to force the pawls into engagement with the tooth disc via movement in a vertical plane. Owing to the shape, size and positioning of the pawl and tooth disc components relative to one another, and the vertical movement of the pawl members into engagement with the tooth disc, the apparatus of the present invention is capable of locking the hall screw in position at any point along the length of the ball screw, even if the pawls are out of alignment with the teeth, or recesses between adjacent teeth.