The ancient Egyptians guaranteed a perfect right angle with no tools at all
Ancient Egyptian surveyors, called 'rope-stretchers', needed to lay out perfect right angles for temples and fields without a protractor, square, or any measuring instrument beyond a length of rope. How could a single knotted rope, pulled taut by a few people, guarantee an exact 90-degree corner every time?
Reveal the answer
They used a rope with 12 evenly spaced knots, forming 12 equal segments. Pulled into a triangle with sides of 3, 4 and 5 segments, the corner between the '3' and '4' sides is always exactly a right angle — because 3-2 + 4-2 = 5-2, the smallest whole-number solution to the Pythagorean theorem. No calculation was needed on site, just the rope and the ratio.