Table 6-1. Screws Used in the Printer Drawing and Description Purpose Used to fasten metal to metal when good electrical contact is needed. Threaded Phillips with captive star washer Used to fasten metal or plastic to plastic mainframes. Silver Self-tapping Phillips screw Used to fasten metal or plastic to plastic mainframes. Black Self-tapping Phillips screw Used to fasten metal or plastic to threaded plastic or metal. Threaded Phillips screw with lock and flat washer 6-4 Removing and Replacing Parts