In measuring the squareness of a rectangular or square form, which dimension should be measured?

Measuring the squareness of a rectangular or square form involves assessing whether the angles of the shape maintain a perfect 90 degrees. The most effective way to determine this is by measuring the diagonal dimensions of the shape. When you measure both diagonals of a rectangle (or square), if they are of equal length, it indicates that the shape is square or rectangular, as the diagonals should bisect each other at the right angles in such geometrical figures.

This method relies on the properties of right triangles, where the lengths of the sides can be compared to confirm right angles. Therefore, when both diagonal measurements equal each other, it serves as a strong indicator that the figure is accurately squared. The other dimensions—length, width, and height—do not provide the necessary assurance regarding the right angles between adjacent sides.