If your sink pop-up won't pop up or seat properly, fixing it is quite easy'usually just a matter of adjusting a few parts. The culprit is often a buildup of hair around the base of the stopper or the pivot rod mechanism. Or, the clevis (see the illustration at right) may be out of adjustment. Here's how to fix it:

1) With a slight twist, try to lift out the stopper. If it seems to be linked to the mechanism, reach under the sink and unscrew the pivot rod retaining nut and pull out the pivot rod to disengage it.

2) Lift the stopper from the drain. Clean off all hair and debris. If the stopper is broken or its seal looks worn, replace it.

3) Face the hole at the bottom of the stopper toward the pivot rod's location, and drop the stopper back into the drain hole. Insert the pivot rod so that it engages the hole in the bottom of the stopper, and tighten on the retaining nut with the stopper in its up position.

4) Loosen the set screw on the clevis, and adjust the strap up or down so that it operates the pivot rod to open and close the stopper. Retighten the set screw.