When I was a young boy, the kids in my neighborhood built a clubhouse. We were able to get the floor level, but we were having trouble making the sideboards fit because we didn't use a plumb line. The finished product looked like the Leaning Tower of Pisa.

Carpenters often use a plumb line to make sure walls are square with the floor. It is a string with a weight on it that hangs straight down to guide the builder when he puts up a wall.

In Amos 7, we read about another kind of plumb line. The Lord first told Amos about a swarm of locusts and a great fire, which were pictures foretelling the destruction of the northern kingdom of Israel. After the prophet prayed and the Lord agreed to delay His judgment, Amos was given a vision of a straight wall. The Lord was standing by it with a plumb line. Because Israel's conduct didn't "square" with God's laws, they experienced God's wrath (vv.8-9).

As followers of Jesus Christ, we have a plumb line by which we can evaluate our lives. It is the Word of God with its principles and commands. When faced with moral choices, we must see what the Scriptures teach. When we follow the Lord's directives, we need not fear what His plumb line will reveal in our lives.
  — David C. Egner