(Still Unanswered) CFrame is not working correctly, doesnt "spawn" the part at the desired area?

In my script I am trying to use CFrame to spawn an Instance.new onto the leg.

I will include the FULL script and the parts only directly related to the Cframe. Also, below the fool script is also an explanation about what im trying to do (if you wanna know)

Full Complete script that contains tool variables and functions ETC

local Player = game:GetService("Players").LocalPlayer
local Mouse = Player:GetMouse()
local tool = script.Parent

tool.Activated:Connect(function()

    wait(0.1)
    local MouseTargetParent =  Mouse.Target.Parent
    print(MouseTargetParent)
    local HumanoidFinder = MouseTargetParent:FindFirstChild("Humanoid")
    if HumanoidFinder.Name == "Humanoid" then
        local leg = HumanoidFinder.Parent:FindFirstChild("LeftLowerLeg")
        local Tie = Instance.new("RopeConstraint")
        local Rock = Instance.new("Part", workspace)
        local AttachmentBase = Instance.new("Attachment")
        local AttachmentSide = Instance.new("Attachment")

        Tie.Parent = MouseTargetParent:FindFirstChild("LeftLowerLeg")
        AttachmentBase.Parent =  MouseTargetParent:FindFirstChild("LeftLowerLeg")
        AttachmentSide.Parent =  Rock
        Rock.CFrame = CFrame.new(leg,leg,leg)
        Tie.Attachment0 = AttachmentBase
        Tie.Attachment1 = AttachmentSide
        Tie.Length = 1000
        Tie.Visible = true


    else do
            print("e")
            return


        end
    end

end)

That is the full script that has everything inside it, the purpose is so that when you click someone, a rope gets tied to their legs with a rock as the thing its tied to, in this instance, a rock,

Secondly, The Condensed version (basically a TLDR, Also includes the variables for the attachments + rope!)

tool.Activated:Connect(function()


        local leg = HumanoidFinder.Parent:FindFirstChild("LeftLowerLeg")
        local Tie = Instance.new("RopeConstraint")
        local Rock = Instance.new("Part", workspace)
        local AttachmentBase = Instance.new("Attachment")
        local AttachmentSide = Instance.new("Attachment")

        Tie.Parent = MouseTargetParent:FindFirstChild("LeftLowerLeg")
        AttachmentBase.Parent =  MouseTargetParent:FindFirstChild("LeftLowerLeg")
        AttachmentSide.Parent =  Rock
        Rock.CFrame = CFrame.new(leg,leg,leg)
        Tie.Attachment0 = AttachmentBase
        Tie.Attachment1 = AttachmentSide
        Tie.Length = 1000
        Tie.Visible = true