Abstract: Screw driving apparatus in which a slide is movable back and forth on a support and is formed with a chute extending in the slide away from the support toward an open end of the chute, and with an access opening to the chute. A driver is mounted on the support for rotation in the chute and for movement in the chute toward and away from the open end in response to the back-and-forth movement of the slide. The slide carries a control plate capable of limited movement relative to the slide between two terminal positions spaced in the direction of slide movement. Two jaws are pivotally mounted on the slide and may jointly obstruct the open end of the chute. A jaw operating member on the control plate engages the jaws and moves them toward and away from the chute-obstructing position in response to movement of the control plate between its terminal positions which is caused by motion transmitting elements on the support when the slide moves back and forth.