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Get To Know Your Level

So you want to establish a straight line. Whether you’re hanging a gallery wall or remodeling your home, a level is an essential tool to ensure your project both looks great and is structurally sound. Let’s get centered.

Level, Plumb & Square

A level isn’t a lone wolf—read on to get the full picture straight (and then get it hung correctly, too!)


True horizontal. Speaking relative to the broader horizon or perpendicular to the gravitational pull of the earth, level simply means both ends of an object rest on the same horizontal plane. If a round object rests on a plane, it will stay put if the plane is truly level. Level can also be used when referring to an intentional pitch that is “off level” from the horizon.


True vertical. In this case, completely perpendicular to the horizon. In house building, the framing should be “very plumb” for maximum strength. If it is not plumb, it can cause buckling and kicking out.


Two intersecting surfaces coming together at a 90 degree angle relative to each other, such as where one wall meets another, or a wall meets a floor.

Types of Levels

Spirit (Bubble) Level

Its mystical moniker comes not from otherworldly guidance toward a straight line, but rather the mineral solution inside the bubble vial. This solution is usually yellow in color and often UV safe. The vial containing the liquid is slightly curved, so when the tool is completely horizontal, the bubble will come to rest in the exact middle of the vial. The less curved the vial, the most accurate your reading will be. Some models feature a magnetic strip on the ends to give a third hand when working with metal surfaces.

Sub Types

Box: With a rectangular, box-shaped frame, often with grips for handling and a milled measuring edge. 

I-Beam: A slightly less sturdy, but more cost effective version of the heftied box level. 

Torpedo: so named for their tapered, torpedo shape. Usually less than a foot long to keep in a toolbelt or pocket, and meant to find level in smaller spaces.

Laser Level

Newer on the scene, a laser level uses lasers to establish both horizontal and vertical lines on a flat surface.

Optical Level

Most often used on construction sites, optical levels allow you to establish straight lines over vast distances with ease.


Don’t try to remodel your home with an iPhone level app—but for hanging a painting, your pocket tech will work in a pinch.

How to confirm your bubble level is… level (and plumb)

Simply place your level against a wall horizontally so that the bubble in the vial is in the center of your gauge lines. Make a tick mark with a pencil (or painter’s tape). Then, make a line at the end of both sides of the level, about an inch from the edge. 

Keeping the level in the same direction (so up remains up, and isn’t turned upside down), rotate the gauge, end-to-end, so that it is once again flush with your center tick mark and two end reference lines. The bubble in the vial should, once again, be fully in the center of the gauge lines. 

The same method works for plumb, but again, do not flip so the bottom is now the top and the top is now the bottom. Simply rotate so you are measuring every bubble vial against itself. 

The Plumb Bob: Used by ancient civilizations for building, a plumb bob is a dummy weight hanging on a string that uses gravity to find “plumb” with the pointed tip once it stops moving. A plumb bob is especially useful when trying to find plumb and level in an empty space.


Romans are thought to have invented the first form of a spirit level, whereby they filled vessels and tanks with water to build their famous aqueducts. It wasn’t until many centuries later, in 1661, that French scientist Melchisedech Thévenot invented the modern bubble level as a telescopic tool. It wasn’t until the mid-19th century it became a part of the carpenter’s tool we know and use today.

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