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How to Measure an Angle With a Speed Square

A speed square can be used to determine virtually any angle.
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A speed square is essentially a triangle-shaped ruler used for calculating angles or as a straight edge. A speed square has a lip on one of its sides that allows you to place it up against the edge of a board or other piece of material for accurate measurements. One of the corners on the lipped edge is called the pivot point, and this is the starting point where all measurements are determined.

Place the speed square along the edge of a board, or the edge of any piece of material. Hook the speed square lip over the edge.

Draw a line from the pivot point directly along the straight edge of the speed square. This line, which is perpendicular to the material edge that the speed square lip is hooked onto, is a 90-degree angle. The straight edge where the pivot point begins will always be used to compute and determine angles.

Pivot the speed square along the pivot point and observe the markings on the opposite side of the square. The markings will be labeled on the speed square as "degrees," and each one of these degrees corresponds to a different angle.

Stop the pivot point at a certain "degree" mark. As an example, pivot the speed square until the numeral 30 aligns with the opposite edge of the piece of material. Draw a line down the pivot point edge of the speed square, on the exact same side that the 90-degree line was drawn. Now that the square has been lined up on the 30-degree mark, however, the angle drawn will be a 30-degree angle. Each time a different degree mark is lined up on the opposite side of the piece of material, the angle is drawn down the pivot point side of the square.

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