Step 5 · Install the New Mounting Assembly
Take a small amount of plumber's putty and roll it into a snake-like rope about 1/2-inch thick. Press this rope firmly around the underside of the new sink flange (the metal drain piece). From the top of the sink, press the flange down securely into the drain opening, so the putty oozes out. From underneath the sink, slide the fiber gasket, then the backup flange, and then the mounting ring over the bottom of the sink flange. Secure it by attaching the snap ring. Finally, tighten the three mounting screws evenly and firmly with a screwdriver. This will pull the assembly tight against the sink. Wipe away the excess putty from inside the sink with a rag.