Albert Barnes Commentary 2 Kings 21:13

"And I will stretch over Jerusalem the line of Samaria, and the plummet of the house of Ahab; and I will wipe Jerusalem as a man wipeth a dish, wiping it and turning it upside down." — 2 Kings 21:13 (ASV)

The general meaning is clear, but the exact force of the metaphor used is not so obvious. If the “line” and the “plummet” are “symbols of rule” or law, the meaning is this: “I will apply the exact same measure and rule to Jerusalem as to Samaria; I will treat both alike with strict and even justice.”