The script is in StarterCharacterScripts, it's not a local script.

I want to add a custom device on players' back. But somehow it doesn't show up in the game.

Here, this is the script:

local ISAC = game.ReplicatedStorage.miniISAC
local char = script.Parent
local players = game:GetService("Players")
local player = players:GetPlayerFromCharacter(char)

player.CharacterAppearanceLoaded:Wait()
local a1 = ISAC:Clone()
local kalp = a1.PrimaryPart
kalp = a1.Kalp
local WELD = Instance.new("Weld")
WELD.Part0 = kalp
WELD.Part1 = char.HumanoidRootPart
a1.PrimaryPart.CFrame = char.HumanoidRootPart.CFrame * CFrame.new(-5,0,-5)
WELD.C0 = char.HumanoidRootPart.CFrame
WELD.C1 = a1.CFrame
a1.Parent = game.Workspace 

Anybody can help me doing this properly?