n Plastic parts may be joined to others by many methods. Self-tapping screws are made with special thread designs to suit specific resins. Threaded inserts to receive mounting screws may be molded in or installed by press-fitting or by means of self-tapping external threads. Press-fitting may be employed to join plastics to similar or dissimilar materials. Snap-fit joints are made by molding or machining an undercut in one part, and providing a lip to engage this undercut in the mating component.