Angle iron is a long strip of steel with two sides perpendicular to each other and forming an angle shape. There are two types of angles: equilateral angle steel and unequal angle steel. The two sides of an equilateral angle steel have equal widths. Its specifications are based on the width of the edges × Edge width × The thickness of the edge is expressed in millimeters. As in "ě 30" × thirty × 3 refers to an equilateral angle steel with an edge width of 30 millimeters and an edge thickness of 3 millimeters. It can also be represented by a model, which is the number of centimeters of the edge width, such as {3 #. The model does not represent the dimensions of different edge thicknesses within the same model. Therefore, in contracts and other documents, the edge width and edge thickness dimensions of the angle steel should be fully filled in to avoid using the model alone. The specifications of hot-rolled equilateral angle steel are 2 # -20 #. Angle steel can be used to form various load-bearing components according to different structural requirements, and can also be used as a connecting element between components. Widely used in various building and engineering structures, such as beams, bridges, transmission towers, lifting and transportation machinery, ships, industrial furnaces, reaction towers, container racks, and warehouses