Upon a wall made by a plumb-line— Literally, Upon a wall of a plumb-line; or, erected by a plumb-line, in order to be perpendicular and firm. God is exhibited in this vision, as erecting, or as repairing Israel, like a wall, that it might not fall into ruin. For the kingdom of Israel had stood hitherto by the providence of God alone, though given to idolatry; and had been repaired under the reign of Jeroboam the second. Afterwards, in the next verse, the Lord denounces that he would let down, or give up the plumb-line in Israel; for so it should be translated; that is, that the kingdom of Israel should be given up by him to their own counsels and strength; and that he would no more pass by among them, to repair and re-establish them. See Houbigant.
Related Commentaries of Amos 7:7
Amos 7:7
7 Thus he shewed me: and, behold, the Lord stood upon a wall made by a plumbline, with a plumbline in his hand.