how are "ButtonUp" events used?

I don't understand how an action like "LBUTTON_UP" is used. I've been playing with it for a while, and doesn't a "LBUTTON_DOWN" event have to come first? If that's the case, there would be an unwanted action (LBUTTON_DOWN) occurring before every up action, right?

The wheel actions I totally get, since the wheel scrolls up and down, both of those actions are physically independent of each other.

Someone please explain to me how to have separate BUTTON_UP and BUTTON_DOWN actions which can peacefully co-exist with each other. Thanks in advance for any help!

There are several button events Windows will send, depending exactly what your fingers do. You should always get button-down followed by button-up, and you might get button-click or even button-doubleclick depending on the delay, etc.

In Strokeit you could conceivably attach different actions to button-down and button-up but I think that would prove unreliable. I generally use button-up only.