How to use cast iron right angle ruler level precautions

Pay attention to the consistency between the temperature of the cast iron square and the workpiece when using it, and do not measure workpieces that are too cold or too hot. Do not hold the square in your hand for a long time. When measuring, attention should be paid to the placement of the angle ruler, which should not be skewed. The angle ruler should be placed in a plane perpendicular to the intersection of the two sides forming a right angle, that is, vertically close to the measured workpiece, otherwise measurement errors will occur