Protection? Manual, page 75

[happygeek]

In the manual, page 75, you can read that from the damage roll an attacker rolls, the protection value "at hit location" is subtracted.
Yet nowhere is it mentioned where this is determined. I am confused.
I can see that I have body armor, and my helmet gives me head protection -- but how do you know if a strike comes to the head, body, feet, or somewhere else? Is this a random chance? Can you do called shots, like in Fallout? I would be grateful for some information regarding how this works. Thank you kindly!