1. IN AN APPARATUS OF THE TYPE DESCRIBED INCLUDING MEANS FOR CONVEYING SUCCESSIVE SCREWS FROM A LOADING STATION ALONG A PREDETERMINED PATH OF TRAVEL; A COMBINATION COMPRISING OF A MECHANISM DISPOSED ADJACENT SAID LOADING STATION FOR FEEDING SCREWS TO THE CONVEYING MEANS, SAID MECHANISM COMPRISING CHUTE MEANS EXTENDING DOWNWARDLY AND HAVING A LOWER END DISPOSED ADJACENT SAID CONVEYING MEANS, A ROCK SHAFT PIVOTALLY MOUNTED ADJACENT SAID CHUTE MEANS, A PLATE MEMBER CARRIED BY SAID SHAFT AND NORMALLY CLOSING THE LOWER END OF SAID CHUTE MEANS FOR SUPPORTING A LOWERMOST SCREW IN THE CHUTE MEANS, AN ELEMENT SHIFTABLY MOUNTED FOR MOVEMENT FROM A RETRACTED POSITION TO AN EXTENDED POSITION IN SAID CHUTE MEANS AND BETWEEN A LOWERMOST SCREW AND AN IMMEDIATELY ADJACENT SCREW IN THE CHUTE MEANS, MEANS INDEPENDENT OF SAID SHAFT FOR NORMALLY YIELDABLY BIASING SAID ELEMENT TOWARD THE RETAINING SAID ELEMENT IN THE RETRACTED POSITION, AND MEANS INTERCONNECTED WITH SAID SHAFT FOR POSITIVELY SHIFTING SAID ELEMENT TO SAID EXTENDED POSITION WHEN THE SHAFT IS ROTATED TO SHIFT SAID PLATE MEM-