How do I make an arm stay at its side while a tool is equipped?

So I have a tool that I am trying to weld to the back of the torso. I want this to happen when a button on a GUI is pressed. This GUI is already coded to only appear when a tool is equipped. My only problem is that when I weld the tool to the back of the torso, the right arm of the character follows. I don't want this so how can I make it so the arm stays at the side of the character, just as if the character didn't have a tool equipped? Here's the code I use to weld the tool to the side of the character:

local torso = character.Torso
local handle = character:FindFirstChild("Lantern").Handle
local weld = Instance.new("Weld")
weld.Name = "BackWeld"
weld.Part0 = torso
weld.Part1 = handle
weld.C0 = CFrame.new(-1,-1.02,0.5)
weld.C0 = weld.C0 * CFrame.fromEulerAnglesXYZ(math.rad(-170),math.rad(-180),-20.5)
weld.Parent = handle

You can do something like this:

tool.Equipped:connect(function()
    local partToFix = tool.GripPart 
    local weld = Instance.new("ManualWeld", partToFix)
    weld.Part0 = tool.Parent.RightHand
    weld.Part1 = partToFix
    weld.C0 = CFrame.new(0,-.5,-.5)
end)

tool.Unequipped:connect(function()
    weld:Destroy()
end)

Source

You can also just make a stationary animation and play it while the user has the tool equipped.