Dragging & resizing?

I work in Flash all day. As y’all know, there’s a feature where you can, say, if you create a square and want to drag its size to be wider, you can either hold down nothing, which makes BOTH sides of the square widen equally, or if you hold down SHIFT, it’ll widen only from the side that you’re grabbing. Very convenient!

Except when it’s not.

SOMETIMES, it seems, you have to hold ALT. Other times, holding down nothing at all will make it widen from one side. And it also seems to vary by whether you’re stretching something vector, drawn natively in Flash, or stretching a photo, which you’ve imported and turned into an MC. They always seem to be the opposite. It works the other way.

I would bet that, literally 88% of the time, I choose the wrong key and always, always, ALWAYS end up pressing UNDO and trying again with a different key press. Naturally, this drives me BONKO trying to predict what’s going to happen. WTF! And I’ve been using Flash for bloody YEARS!

What is the rule behind this?