Step 3 · Remove the Sink Strainer
From underneath the sink, use pliers or a strainer wrench to loosen and remove the large mounting nut holding the sink strainer in place. There may be screws to loosen as well. Once the nut is off, push up on the strainer from below to pop it out of the sink drain opening. Use a plastic putty knife to scrape away all of the old, hardened plumber's putty from the sink's surface. Clean the area thoroughly with a rag and a cleaning solvent if necessary.