The Mayan people used a clever way to construct right angles. Start with a cord with eight knots, dividing it into seven equal segments with a knot at each end. There are loops at each of the knots for staking to the ground.
Since the knots are evenly spaced, when knots 1 and 4 are held together and the cord is pulled taut, an equilateral triangle with interior angles of 60° is formed. Then knot 6 is joined with knot 3 and the cord pulled tight resulting in another equilateral triangle formed by knots 4, 5 and 6. Finally knot 8 is joined with knot 5 forming a third equilateral triangle (and all together, half of a hexagon). If one runs a ray (or rope) from knot 1 through knot 2 and another ray from knot 1 through knot 7, the resulting angle is a right angle.