How do I check if player has certain UserId?

I cannot seem to make the script check if the player's UserId is correct.

Here is my code:

local Players = game:GetService('Players')
local Player = Players.LocalPlayer

if script.Parent.PrimaryPart then
    if Player.UserId == 171275787 then
        for i, v in pairs(script.Parent:GetDescendants()) do
            if v:IsA("BasePart") then
                if v ~= script.Parent.PrimaryPart then
                    local wc = Instance.new("WeldConstraint",script.Parent.PrimaryPart)
                    wc.Name = "weld"
                    wc.Part0 = script.Parent.PrimaryPart
                    wc.Part1 = v
                    v.Anchored = false
                    v.CanCollide = false
                    v.Massless = true
                end
            end
        end

        script.putBehind.Disabled = false
    end

end

Please help, Thanks