How to Use a Tailor's L-Square

Place your pattern on a piece of pattern paper. Hold the pattern firmly with your non-drawing hand, and use your pencil in your drawing hand to trace around the outside of the original pattern. Store the original pattern for the time being.

Find the scale measurement on the ruler to which you want to scale your pattern. Each scale will be labeled accordingly to make it easier to find the correct scale.

Place the ruler with your scale directly on the first seam of the pattern. Line up the ruler with the line of the seam exactly. Place the zero point or beginning of your scale on your ruler at the bottom of the seam line. For example, the zero point for the 16th scale may be several inches up the square. Move the ruler along the seam line until the zero point is at the beginning of the seam.

Read the original measurement of the seam you are about to scale. Draw a line from the zero point to the measurement on the tailor square. For example, if your measurement is 12 inches, and you are scaling your pattern down to quarter size, draw a line from the zero point to 12 inches. This creates a 3-inch-long line or a quarter of your original measurement.

Repeat the scaling with all of your seams. Use the proper scale with each seam. Use the ruler edge to connect the lines of your seams to finish your scaled pattern.