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Plumb Bob – Everything You Need to Know

The plumb bob might not be the most exciting or innovative tool out there, but it’s undoubtedly one of the most useful.

As with a spirit level, the primary purpose of a plumb bob is to check the alignment of various elements during construction or DIY.

Whereas spirit levels are handy for checking vertical, horizontal, or angled alignment at various localized points though, the plumb bob is much better-suited to confirming vertical alignment over much greater distances, for example, over the height of an entire wall.

Plumb bobs are as simple as they look, too, mainly consisting of a piece of string and a weight as shown below.

an image showing a Plumb Bob in use

There are no fiddly settings to worry about, either. Hang the plumb bob clear of the ground, wait for it to stop swinging, and thanks to the power of gravity, you’ll be able to tell exactly where plumb is.

So, if you need to check vertical alignment quickly and easily over long distances, for example, when building a wall, constructing a fence, hanging a door, painting vertical lines, or when hanging wallpaper, the plumb bob could be just the tool for you.

Despite how handy they are, though, a lot of people won’t have a plumb bob in their toolbox.

Thankfully, as you’ll see later on in this article, they’re incredibly easy to make, and we’ll show you how step-by-step.

So, without further ado, here’s everything you need to know about the humble plumb bob…

Quick Links

What is a Plumb Bob?

What Is a Plumb Bob Used For?

How to Make a Homemade Plumb Bob – 3 Simple Steps

How to use a Plumb Bob

What is a Plumb Bob?

As mentioned, a plumb bob, or as it’s commonly referred to, a plumb line, consists of a pointed weight attached to a piece of string, and it uses gravity to show the user where ‘plumb’, or vertical alignment, is.

They’re used to check vertical alignment over long distances, for example, across the entire height of a wall, or to transfer points over long distances where measuring would be inconvenient, for example, to find a spot on a floor relative to a specific location on a ceiling.

They certainly aren’t a new technology, with evidence linking their use back thousands of years to ancient Egypt and construction of the pyramids.

What Is a Plumb Bob Used For?

Here are some of the most common uses for a plumb bob:

  • Transferring Points From Ceiling to Floor/Worktop
  • If you’ve ever tried to match a point on a ceiling to a spot on the floor, you’ll understand how difficult this can be if you aren’t using a plumb bob.

    Rather than relying on measurements from a common point, for example, a wall, it’s much easier to hang a plumb bob from the ceiling, letting gravity show you the location of the relative spot on the floor.

    A real-world example could be using a plumb bob to ensure that a downlight will be perfectly centered above a kitchen island before drilling.

  • To Maintain Vertical Alignment of Walls During Construction
  • By hanging a plumb line beside where a brick wall will be built, for example, the bricklayer can ensure that they correctly align the current layer of bricks before moving on to the next.
  • Keeping Wallpaper Vertical While Hanging
  • Most walls in houses aren’t entirely plumb. Because of this, you can’t rely on working from the edge of the wall and simply matching up the wallpaper lines as you work your way across.

    Hanging a plumb bob, marking a few points along the length of the plumb line, and then connecting these using a straight edge will give a far more accurate representation of plumb that you can use to hang the wallpaper entirely vertical.

  • Keeping a Door Vertical While Hanging
  • A handy alternative to a spirit level, the Plumb Bob will help you check the verticality of the door while hanging to prevent any rubbing on the floor, uneven gaps, and a door that won’t latch.

How to Make a Homemade Plumb Bob – 3 Simple Steps

Need a plumb bob, but don’t have one to hand?

Don’t worry, owing to how simple they are, they’re incredibly easy to make.

So, before you go off and buy one, check out the following steps to learn how to make a homemade plumb bob in just a few minutes.

Here’s what you’ll need:

  • 1x screwdriver
  • 1x ring pull from drink can
  • 1x length of string

homemade plumb bob materials image

Let’s get started…

Cut String to (Approx) Required Length
The first step is to measure the height of wherever you’ll be using the plumb line.

Whatever length you measure, add an extra four or five inches to cover the pieces of string that you’ll lose when tying on the screwdriver and ring pull.

homemade plumb line step one image

Go ahead and cut the string to the required length.

Tie String to Screwdriver/Ring Pull
Tie one end of the cut piece of string to the screwdriver. Leave a bit of slack in the string below the knot, as if it’s overly tight it can affect the alignment of the screwdriver as it hangs.

For this example, we’ve chosen a screwdriver with a hole in the handle. We wouldn’t recommend using one without a hole and simply tying the string around the handle, as this will more than likely affect the alignment.

Next, take the end of the piece of string and hold it against the point where you’ll be securing the plumb line once complete. The tip of the screwdriver should hang about one inch from the floor (you might need to trim the unused end of the string to allow this).

making a simple plumb bob - step two image

Finally, go ahead and tie the ring pull to the unused end of the string as shown above.

Hang Plumb Bob Wherever Required
To use the plumb line, attach the ring pull to a nail, screw, or whatever else you want to use to hold it in position.

It’s worthwhile bouncing the screwdriver a few times on the string to make sure its alignment isn’t being affected by the line.

making a plumb bob - step three image

Finally, wait for the string and screwdriver to stop swinging before using them to test for plumb.

How to Use a Plumb Bob

There are a couple of different ways to use a plumb bob:

When Transferring Points From Floor/Worktop to Worktop

  1. The first step is to mark a position on the floor or worktop. Let’s assume that you want to fit a downlight that is centered over a kitchen island, so in this case, you’d mark a point at the very center of the island.
  2. Next, carefully using a ladder, take the end of the plumb line and hang the weight until it rests directly over the mark at the center of the worktop.
  3. Ensure the plumb bob still hangs over the center point even after it stops swinging. Once verified, mark the position on the ceiling at the top of the plumb line. The location you’ve marked corresponds to where the center of the downlight will need to sit when fitted.

When Checking Vertical Alignment in Walls & Doors Etc.

  1. Either hammer in a nail or insert a screw into a horizontal surface that sits perpendicular to the vertical surface of which you want to check the vertical alignment. For example, to check that a new stud wall is vertically aligned, hammer the nail or insert the screw into a ceiling joist (ideally about an inch away from where the top of the stud wall will sit once installed).
  2. Next, tie the end of the plumb bob to the nail or the screw, ensuring that the plumb weight sits clear of the floor by a couple of inches.
  3. Wait for the plumb wait to stop swinging. Measure the distance between the plumb line and stud wall from a point close to the top of the plumb line. Repeat the process at the bottom of the plumb line.
  4. Compare the figures, adjusting the stud wall and repeating the measurements until the top and bottom figures match, at which point you’ll know that the stud wall is plumb.

Final Remarks

We hope that you found this article useful.

If you’ve decided against making a homemade plumb bob, hopefully, we’ve done enough to convince you of the merits of buying one instead to keep in your toolbox.

In all honesty, not only are they relatively cheap to buy, they’re simple to use and a doddle to set up, too. Hence, there’s no excuse not to make/buy and use a plumb bob if you’re in any way concerned with the quality and accuracy of whatever construction or decorating work you tackle.

Feel free to drop us a comment below if you have any other questions or queries.

Good luck!

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Author: Jon Maxwell
Senior Writer, ToolCrowd
Jon Maxwell writes about various topics for ToolCrowd, including tool reviews, material advice, common home problems, and general DIY advice and how-to articles. His work has been published in national publications for audiences including consumers, homeowners, and industry experts. Jon has a bachelor's degree in Building Surveying and a master's degree in a branch of Civil Engineering focusing on concrete and steel durability. When he isn't writing for ToolCrowd, Jon enjoys completing DIY tasks in his own home, as well as woodworking in his home workshop, snowboarding, and website development. Contact Jonarrow_right_alt