Step 2 · Install Drain Assemblies
Carefully place the new undermount sink upside down on a protected surface, like a piece of cardboard on the floor. First, install the basket strainer for the non-disposal side. Apply a rope of plumber's putty around the underside of the strainer's flange, press it firmly into the drain opening from inside the sink bowl. From underneath, place the rubber gasket, fiber washer, and threaded locknut. Tighten the locknut by hand, then use channel-lock pliers or a strainer locknut wrench to give it a final quarter-turn. Clean up any excess putty that squeezes out. For the disposal side, install the garbage disposal mounting flange following the manufacturer's instructions, which is a similar process but typically uses a different set of gaskets and a snap ring.