To rig an arm is easy if we just limit to bend the elbow.
Trying to twist and stretch it is more challenging anyway !
And moreover, at the end of the arm there's the hand: a little more complex structure to control because, you know, it has digits.
And we're lucky that humans just have 5 of them !
We'll see, of course, how to rig the hand as well and how to recall quickly some poses of common use, such as the first and the spread hand.
If you enjoy this chapter just wave your hand !