Thus he showed me
A third vision, which was in the following manner: and, behold, the Lord stood upon a wall [made] by a plumbline, with a
plumbline in his hand:
this "wall" was the people of Israel, who were built up as a wall, firm and strong; and so stood against their enemies, while supported by the Lord, and he stood by them. The Septuagint version is, "an adamantine wall". In their constitution, both civil and ecclesiastic, they were formed according to the good and righteous laws of God, which may be signified by the plumbline; and so the Targum renders it, "the wall of judgment". And now the Lord appears standing upon this wall, to trample it down, and not to support it; and with a plumbline in his hand, to examine and try whether this wall was as it was first erected; whether it did not bulge out, and vary from its former structure, and was not according to the line and rule of his divine word, which was a rule of righteousness.
The Brenton translation of the Septuagint is in the public domain.