Determine where the player's aiming at on the body

Hi,
I want to be able to determine if the player's aiming at the target's head, hand, chest,etc. how can this be done?
I looked at PlayerData in server/script/Player.cs and this jumps out:
// Damage location details
boxNormalHeadPercentage = 0.83;
boxNormalTorsoPercentage = 0.49;
boxHeadLeftPercentage = 0;
boxHeadRightPercentage = 1;
boxHeadBackPercentage = 0;
boxHeadFrontPercentage = 1;

but I am not sure what they do. any docs or suggestions are appreciated.
thanks!