'Plumbline' in the Bible

Thus did he shew unto me; and behold, the Lord stood upon a wall made by a plumb-line, with a plumb-line in his hand.

And Jehovah said unto me, Amos, what seest thou? And I said, A plumb-line. And the Lord said, Behold, I will set a plumb-line in the midst of my people Israel: I will not again pass by them any more.