How to Find Square Layout Lines

If laying out square lines is part of your next home improvement project, here’s a great way to do it using the Pythagorean theorem (A² + B² = C²) to form a right angle triangle with 3′ and 4′ sides and a diagonal of 5′:

  1. Establish a 4′ line parallel to a wall.
  2. Measure out 3′ from one end of the 4′ line roughly perpendicular to it.
  3. Hold a tape measure on the other end of the 4′ line.
  4. Measure 5′ so it forms a triangle with the end of the 3′ line.
  5. Adjust the angle of the 3′ line until the tape measure aligns with it.