A combination square has a built-in bubble level. See more pictures of hand tools.

Most homeowners and renters rarely use a square. However, woodworkers, carpenters, and builders use them frequently. Selecting the right one for the job is easy.

What a Square Does

The main purpose of a square is to ensure that components are perpendicular, or at right angles to each other. In addition, most squares serve as measurement rulers marked in inches, fractional inches, and sometimes in centimeters and millimeters.

Large framing squares, also called carpenter squares, are used in building cabinets and homes. Speed squares, sometimes referred to as try squares, are smaller and include additional angles for measurement. Combination squares have a ruler blade with an adjustable sliding stock to measure 90-degree and 45-degree angles. Combination squares include a built-in bubble level that is useful for leveling small components such as picture frames.

How to Safely Use a Square

A combination square is easy to use. Lay the stock against an object edge, then use the nut to loosen and move the ruler as needed. Most combination squares also have a removable pointed pin called a scribe that can be used to mark measurements on the object being squared. Framing and speed squares typically come with instructions for various tasks.

How to Maintain a Square

Maintaining a square is relatively easy. Most important, do not store it where it can become damaged or bent, as accurate measurement is its primary task. Steel squares should be kept clean and dry so they don't rust. Most framing and speed squares now are made of aluminum and, with care, will be useful for decades.

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Tools Related to the Square

Other handy measurement devices include the tape measure and level.

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