Unscrew the nut, pull out the rod, and remove the stopper. Then screw the nut and rod back in place without the stopper.
[header] How to clean a sink trap [title] Remove any sink stoppers. [step] If your stopper has a pivot rod, then you will need to remove this to remove the stopper. Look under the sink and locate a locking nut where the pivot rod goes into the drainpipe.