Hollow section is an object of a certain geometry made of iron or steel and a material having a certain strength and toughness (such as plastic, aluminum, glass fiber, etc.) by rolling, extrusion, casting and the like. Including angle steel, channel steel, I-beam, square steel, H-beam, etc.is an object of a certain geometry made of iron or steel and a material having a certain strength and toughness (such as plastic, aluminum, glass fiber, etc.) by rolling, extrusion, casting and the like. Including angle steel, channel steel, I-beam, square steel, H-beam, etc.