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How to Create Perpendicular Lines

Perpendicular lines intersect each other to create four 90-degree angles. While it would be fairly easy to create some lines that are roughly perpendicular, if you want to create perfectly perpendicular lines, you will need a ruler and a compass. Once you have these, you can quickly create two line segments that intersect at exactly 90-degree angles.

Compass
Ruler

Instructions

- 1
  Draw a line with a ruler, and note how long it is in inches or centimeters.
- 2
  Put the point of the compass on one end of the line, and set the radius of the compass so that it is a little bit longer than half the length of the line. Draw a half circle that intersects the line.
- 3
  Do the same thing at the other end of the line so that you have two half-circles that intersect each other at two points.
- 4
  Use your ruler to draw a line between the two points where the circles intersect. This line will be perfectly perpendicular to the other line.

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