Hillman Round Head Machine Screw, 1/4 x 1/2 In. is designed to securely fasten metal parts together, either by using nuts or by screwing directly into a threaded receptacle. The length of the screw is measured from the underside of the head to the tip, ensuring the right fit for your fastening needs. For optimal performance, it is to pair these machine screws with nuts that have the same finish and threading. Model Number: