Reasons for IK Bone's presence in UE4 mannequin

why IK_Hand_Root and IK_Foot_Root are present in UE4 mannequins.
Let me know what this bones plays.
I especially wonder about IK_Hand_Gun…

These are bones you can use for IK setups. Some nodes inside the animation blueprint only take in IK bones for their settings. This allows you to have setups where the hand will always stick to the gun, or feet to the ground. You can learn more about IK here: IK Setups | Unreal Engine Documentation

Thank you for your reply.
I see an example of the Ik-setups guide document.
However, I have confirmed that the ik bone mentioned in the text is not used.
In fact, even if I do not have ik bone
It is possible to attach a hand to a weapon or to express a footplacement.
I can even make weapon swaps naturally when using the ik_hand_gun bone.
But I still do not know where to use ik_hand_r or ik_hand_l.

Correct, you do not have to use those bones, you can also create your own virtual bones for these purposes. You can use them however you want, or even not at all.

Thank you.
I have solved the question.
I hope everything you do is happy. :slight_smile: