Drain plugs seal the openings in oil pans, engine blocks, radiators, transmissions, and differentials to retain fluids. Typically constructed of steel or aluminum, they utilize a threaded design for secure installation and removal during fluid drain and fill procedures. A sealing washer—often copper, aluminum, or a polymeric material—ensures a leak-proof connection. Variations include magnetic drain plugs to capture ferrous particles, and oil drain plugs with extended reach for modified oil pans. Proper torque specification during installation is critical to prevent leaks or damage to the mating surface.