How to Construct a Rectangle Using a Straight Edge & Ruler

Determine the width of your rectangle by placing a ruler on the paper horizontally and making a mark on one end of the ruler. Count farther down the ruler and create another mark. For example, if you made a mark at the "0 inches" on the ruler and another mark at the "5 inches," the width of your rectangle would be 5 inches.

Turn your ruler vertically and line one end of the ruler with the first mark you made. Use a protractor to make sure you have a 90-degree angle, and count down the ruler and make another mark to determine the height of the rectangle. For example, if you counted down 3 inches, the height of your rectangle would be 3 inches.

Place one end of the ruler vertically against the second mark you created in Step 1. Count down the ruler to the same exact distance measured in Step 2, again using a protractor to ensure a 90-degree angle. For example, if you measured 3 inches for the height of the rectangle, you will need to count down the ruler 3 inches before making the mark.

Connect the four marks you have made on the page horizontally and vertically with a straight edge, such as a ruler.

Use a protractor to double-check that all four corners create 90-degree angles. Lay the protractor down with the base against one of the sides. Line up each adjacent line with the curved part of the protractor and read the marking. If the adjacent lines pass through the 90-degree mark on the protractor, the image is a perfect rectangle with equidistant horizontal and vertical lines.