A hole near the end of a sink stopper surrounds the end of the drain's pivot rod. The drain's pivot rod moves the sink stopper up and down when an operator moves the lift rod's handle. A tight-fitting stopper holds water in the sink. Hair build-up around the pivot rod often prevents the stopper from fully seating against the sink's drain hole. Removing the stopper provides access to the pivot rod for cleaning. After removing the hair from the pivot rod, flush the drain pipe with warm water before reconnecting the sink stopper.
Loosen the pivot rod's retaining nut, located behind the drain's tail pipe, with locking pliers. Slide the retaining nut, gasket and pivot rod out of the tail pipe about 1/4 inch. The retaining nut and gasket slide over the end of the pivot rod.
Hold the sink stopper above the drain hole with its hole facing the front of the sink.
Drop the sink stopper into the drain. The part of the sink stopper with the hole should slide between the end of the pivot rod and the inside of the drain's tail pipe.
Angle the clevis-end of the pivot rod up. The clevis is the vertical piece with holes, and it connects to the lift rod. With the clevis-rod-end of the pivot rod angled up, the sink stopper end of the pivot rod is angled down.
Push the pivot rod into the sink stopper's hole.
Hand-tighten the pivot rod's retaining nut, and test the stopper's action with the lift rod. If the stopper moves up and down with the lift rod, tighten the retaining nut with the locking pliers. If the stopper does not move up and down, loosen the retaining nut and realign the pivot rod in the stopper's hole. Retest the stopper.