Is It Plumb, Level, or Square?

Plumb, Level, Square Diagram

We like to check to see if things are on the level – or should we say “plumb”?
Is a wall plumb or level? Is the floor level? Is the door frame plumb or square?

Confusing, isn’t it? Here’s a quick guide to those terms.

“Plumb” refers to vertical surfaces. A foundation wall or doorframe that is “plumb” is perfectly vertical. Plumb can be checked with a level tool that has a bubble floating within a vial. When the tool is placed against a plumb surface, the bubble floats in the center of the markings.

Plumb can also be checked with a plumb bob – a weight hung on the end of a string. A plumb bob will always hang perfectly vertical.

“Level” refers to horizontal surfaces. Whether a surface is a level can be checked with a level tool (but of course!).

“Square” refers to the relative position of two surfaces. If they meet at a 90-degree angle, the two surfaces are square. You can check for square with a carpenter’s square tool. For larger surfaces, builders use a 3-4-5 triangle technique to ensure accurate 90-degree angles.

Just remember: carpenters and other building professionals worry about level, plumb, and square – or your windows and doors would not close.

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