How to use a plumb bob

What does plumb actually mean? And why is this thing named Bob? Let's get after it. Plumb simply means vertical, straight up and down. It comes from the Latin word plumbum, which means lead. Builders used to hang a heavy lead weight from a line. And gravity pulled the weight straight down, giving them a vertical reference. And that's eventually where we got the word plumb for something that's perfectly vertical. And for Bobby you might ask, that's not some dude. That's just the name of the weight at the end of the line. Set your length so the weight hangs freely without touching the ground. Tie your string to a reference point, then just let gravity do the work and wait until the bob stops swinging. Now we can check if this board's actually plumb. First we'll measure from the top, inch and an eighth. The bottom, 8 in. We got to move this 2 by 4 quite a bit that way. Now that we straightened it out, our bottom should read inch and an eighth. And we can check it with our level and it's absolutely plumb. For most jobs I'm grabbing a level, but this is where a plumb bob really shines. Let's say I need to run this vent straight up through the roof. I can hang my plumb bob from the point I want it to come through, let it stop swinging down below, and wherever that point settles, I can mark the point directly below it. This same idea works for laying out posts, walls, framing, and anytime you need a point directly above or below another one. A string, a weight, and some gravity, and a thousand years later, it still works out perfectly. Anyways, I'm going to go hang out with my new friend Bob. I'll catch you guys later. Peace.