This section is from the book "The Carpenters' Guide", by Harvey Miller. Also available from Amazon: The carpenters' guide.
The front wall line, parallel to the street and leveled to grade, remains unchanged.
Rule 1. From the intersection of the lines at the established corners of the building, measure 6' on one line and 8' on the intersecting line and adjust the side line so the hypotenuse, or measurement between 6' and 8' will be 10' (fig. 5). With every ad-
Fig. 5 To Square A Foundation justment of the line, remeasure from the intersection of the two lines until the measurements are exactly 6', 8' and 10' and the lines will be at a perfect right angle or square (fig. 5).
Rule 2. Take a steel tape-line and measure diagonally to the opposite corners, then reverse the tape-line to the two opposite corners, and adjust the lines until the measurements are the same and the lines will be squared.
This rule is reliable in any building where the measurements are taken equal distances on the side lines from the two front corners and both ends of line are the same width.