What Are Level, Plumb, Square & True in Construction and Carpentry?

What Are Level, Plumb, Square & True in Construction and Carpentry?

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If you’re planning on taking up carpentry as a hobby or performing a DIY construction job, then it’s important for you to have the right tools for the job. But at the same time, it’s important for you to also know the language used in both fields before even picking up your tools.

Knowing the language of carpentry or construction can, among other things, help you understand building plans more effectively, leading to a better outcome for your project overall.

Regardless of what you are building, you’ll quickly see that it is important for your work to be as even and balanced as possible. You’ll know that this kind of practical precision is required when seeing words like “level,” “plumb,” “square,” and “true.” But what do each of those words mean on their own?

This guide will help you understand each in the context of construction and carpentry.

What Does “Level” Mean in Construction and Carpentry?

While working on a project that involves horizontal components, your project instructions or guidelines may implore you to “level” that surface before proceeding. In this context, those instructions are communicating the need to make that your surface be perfectly balanced with regards to its horizontal angle.

In other words, a perfectly “level” floor or shelf will not slope in any direction.

Leveling is an essential step in any carpentry or construction project, which is why a specialized tool is used to determine if a surface is truly “level.”

This tool’s name is easy to remember because it is known simply as a “level.” This long, bar-like tool features one or more built-in capsules of liquid, each with a bubble in it. When leveling a surface, these bubbles must fall between the market lines on their enclosure or else the surface is not precisely horizontally even.

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What Does “Plumb” Mean in Construction and Carpentry?

If you are engaged with a wall-building project, your foreman may ask you to “plumb that wall” after setting it upright but before securing it in place.

In this context, your foreman is asking you to ensure that the new wall is vertically even or balanced. In other words, this task will require you to ensure that the wall in question is positioned such that it is perfectly upright from floor to ceiling.

To do that, you’ll need a specialized tool known as a “plumb bob” or “plumb line.”

In most cases, this tool looks like a long string with a pointed metal weight at the end. When a plumb bob is hung from a newly positioned wall, it can be used to determine if that wall is positioned evenly at both its top and bottom. This, in theory, allows a user to determine if that wall is slanted out in any manner.

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What Does “Square” Mean in Construction and Carpentry?

While working on a carpentry project such as a blanket chest, you may come to a point where you need to ensure that the internal corners are vertically and horizontally even.

To do this, you’ll need to “square” those internal corners and ensure that they are as close to a true 90-degree angle as possible. Doing this prevents small discrepancies in the angle of either surface from causing issues later on in the project.

To accomplish this task, you’ll need to grab an easy-to-remember tool known as a “square.”

These can either be a large, L-shaped piece of metal that resembles two joined rulers or a smaller, orange triangle with twin flat legs. To use either, simply place it snuggly against the bottom and side of the target object. If it lays flush against both, you can be certain that both surfaces are “squared” away.

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What Does “True” Mean in Construction and Carpentry?

Typically, to say that something is “true” is to describe its veracity. However, in the context of carpentry and construction, “true” refers to the state of any flat surface or angle. To be specific, a “true” surface is as “plumb” or as “level” as the job requires (which, in most cases, is a perfect level of both or either). In the same vein, a “true” corner would be squared to exactly 90 degrees.

Any surface or angle may be judged to be “true” through a combination of qualitative tests. For example, a newly constructed room may be judged to be “true” only after all of its floors have been leveled and all of its walls have been plumbed. Either the leveling or the plumbing could also be judged to be “true” on their own, but only if they achieve a 0 degree or 90-degree angle, respectively.

Why Is It Important for Things to Be Level, Plumb, Square, and True?

When it comes to leveling, plumbing, and squaring, it is essential that each be fully true. This ensures that every vertical and horizontal surface is perfectly balanced, without any slopes across their entire length.

Sloping of any kind can cause problems, even if that slope is only very minor at first. In the context of large scale construction, a minor discrepancy in the vertical or horizontal angle of a surface can cause the walls and floors of the structure to slant in or outward.

This unevenness can be amplified as a building grows until the building itself is not structurally sound due to the slant of its floors or walls.

What Is True in Construction?


As you can now see, each of these essential carpentry and construction terms can have a major impact on how you proceed with a project. When each term is invoked, you’ll need to take out and use a special tool designed to ensure that that surface is “true” in terms of its angle.

You may even need to repeat your test several times to ensure that every horizontal and vertical angle throughout your project is as structurally sound and fully aligned with one another as possible.