This symbol is a vertical mathematical symbol. Verticality means that when the angle formed by two straight lines is a right angle, it is called perpendicular to each other. This concept can also be extended to the situation between two planes or between a straight line and a plane. Symbol is a symbol used to refer to and represent other things, and it is a symbol of vertical mathematical symbols. When the benchmark is a straight line and the evaluated line is a straight line, the verticality is the distance between the two farthest planes that are perpendicular to the benchmark straight line and contain points on the measured straight line. When the datum is a straight line and the measured plane is a plane, verticality is the distance between the two farthest planes perpendicular to the datum straight line and containing points on the measured plane. When the reference plane is a plane and the evaluation line is a straight line, verticality refers to the distance between two planes which are perpendicular to the reference plane and the evaluation direction, are farthest from each other and contain points on the measured line.