A 3-4-5 system is used to:

The 3-4-5 system is a practical method used in construction and carpentry to check for square corners. By creating a right triangle, where the lengths of the sides are in a 3:4:5 ratio, you can ensure that adjacent walls are at 90 degrees to each other.

To apply the 3-4-5 method, you measure 3 feet along one side, 4 feet along the other, and then check the distance between the two points created at the ends of these measurements, which should be exactly 5 feet if the corner is square. This technique is invaluable in laying foundations, framing, and even in floor covering installation, as it ensures that the structure is correctly aligned.

The other options do not specifically relate to the purpose of the 3-4-5 system. While leveling surfaces or measuring lengths might involve some similar measuring techniques, they do not serve the primary function of verifying right angles in the way that the 3-4-5 system does. Determining area is a separate calculation entirely and is not relevant to the function of checking for square.