How to Find Angles Using a Speed Square

The speed square or rafter-angle square is an extremely versatile tool originally intended to help carpenters quickly and accurately mark roof rafters. It is a triangle-shaped measuring tool and can be used to make cutting lumber fast and accurate, making many projects faster and easier. Follow these steps to find angles.

Step 1: Orient Yourself

The speed square can basically be used as a protractor because it has degree graduations along the diagonal edge, making reading the angles fairly simple. At the corner of the square there is a pivot point. Because the speed square is a 90-degree angle, each line on the diagonal represents 1 degree for a total of 90.

Step 2: Find an Angle

Hold the pivot point against the board and move the square until your desired angle lines up with the edge of the board. It is important to note that the angle you need to find is actually the complement of the angle you need. For example, if you need a 60-degree angle, you need to find the 30-degree mark. This is the complementary angle because the two add up to 90 degrees. After you have found the correct angle, draw a line along the square.

Now that you have gotten more acquainted with the speed square, you may find it more useful than you think. It can be used for many purposes, not just finding angles.