Construction of a Square
1. Construct a line segment.
2. Construct a perpendicular line from a point on the line segment.
3. Draw a circle with one point as the center and the other point as a point on the circle arc.
4. Mark the intersection of the perpendicular line and circle.
5. Construct a line parallel to the original segment.
6. Construct a perpendicular line from the other point on the line segment.