The Egyptians used the plumb bob and triangles of knotted cord.
One of the most difficult problems in building the temples and pyramids was making the base perfectly level. A mistake meant, that the whole pyramid would go crooked. The exact vertical was determined with the help of a string, with a weight hanging from it, with a lot so, certainly. The surface of the floor had to form a right angle to the vertical line.
These builders also discovered, how to use a measuring cord, which periodically from 3,4 and 5 units of measure knots had, could make right triangles; these then served them to build right-angled rooms and wall corners.