Harpedonaptai are more commonly known as the "Rope Stretchers" or the "Rope Knotters". They were employed by the Pharaohs as land surveyors. They used to form right angles with their ropes. Some scholars conjecture that they may have constructed right angles by using a rope consisting of 12 equidistant knots. Such a rope can be spanned into 3-4-5 triangle, which has a right angle according to the converse of Pythagorean theorem.