First of all, sorry for that title. I really couldn't find something better, how to describe my problem in short.
I've drew a lock, you can see it on image:
I would need to create a frame animation, so the lock will end like this:
So the final animation will be similar like this one: dribbble.com/shots/1141621-Lock-Icon-Animation-GIF
Here's my problem: I cannot draw the "bend" on the top of the lock (the U shape). If I distort it in PS, it's just like a paper, it flips, and there's no thickness of the metal "U". And when it comes to drawing, I don't know the angle in which I have to "bend" the "U" shape correctly, so I can't even do it by hand.
How could I draw it, so the final animation would look like the one I've described?