This is a push/pull shower valve that has a stem with the handle attached. Weird, but the stem has a hole down through the middle of it (the length of the stem). The stem has an eccentric cam on one end and a handle on the outside end. When the handle is turned for the hot water, the cam opens the hot water valve and when turned the other way opens the cold water valve. The problem is water comes through the stem and leaks out through the hole where the screw attaches the handle to the stem. I have already put new packing around the stem, but the water continues to leak through the center of the stem. I have never seen a stem with a hole in the center of it until this one started leaking after 30 years.