What does the 3-4-5 method help to check when laying out building lines?

The 3-4-5 method is a practical technique used in construction to ensure that angles are square, typically when laying out building lines. This method is based on the Pythagorean theorem, which states that in a right triangle, the square of the length of the hypotenuse (the side opposite the right angle) is equal to the sum of the squares of the lengths of the other two sides. By measuring a line that is 3 units long, then a line that is 4 units long, and checking that the distance across the diagonal between those two points is 5 units, builders can ensure that corners are formed at a perfect right angle.

This squareness is fundamental in construction as it impacts various aspects of the structure's integrity and alignment, including walls, foundations, and overall aesthetics. A building that is not square may have issues during installation of windows, doors, and other components that rely on precise angles. Thus, using the 3-4-5 method effectively checks the squareness of the building layout before further construction proceeds.