Constraints not working?(taken from the roblox page)

local Rod = game.StarterPack.WoodenFishingRod.Pole2
local attachmentA = Instance.new("Attachment", Rod)
attachmentA.Position = Vector3.new(0, 0, -1)

local Rope = game.StarterPack.WoodenFishingRod.Rope
local attachmentB = Instance.new("Attachment", Rope)
attachmentB.Position = Vector3.new(0, .5, 0)

local rodConstraint = Instance.new("RodConstraint", Rod)
rodConstraint.Attachment0 = attachmentA
rodConstraint.Attachment1 = attachmentB
rodConstraint.Length = 3

while wait(2) do
  rodConstraint.Enabled = not rodConstraint.Enabled
end

(taken from the roblox Joints page)

the constraints are not there. Only the attachments and the parts are not connected. Am I doing something wrong?