A screw - plastic part unit in which the plastic part can be a guide having a tapered bottom end for fitting into a countersink to center the tip end of the screw in the countersink and also can have at least one cut-out portion at its top end to facilitate fracturing of the guide as the screw is threaded into a base member. In one embodiment the screw has a thread between its head and tip end which extends to near the tip end leaving a clear area between the thread end tip end and the part of plastic material molded around the screw clear area in which there can be a circumferential groove or rib finto or over which the plastic part is molded to better hold the part to the screw. In another embodiment fins extend into the part hole to hold the screw by an interference type fit.