[Walt Fricke]

Some of the ball joints have a hole in their head, through which a clip can be inserted. This is a belt and suspenders approach, because (at least when new) the clip inside the cup (not intended to be removed or replaced) normally is all that is needed to keep the cup on the ball. Racers are especially prone to want the cup part with the hole for a clip. You can see the clips in some of the parts diagrams.

If you have one, you need to pull it to pry the cup off the ball. But you can tell by looking and feeling if there is a clip there or not.