The most common structural steel shapes consist of the I-beam, the HSS-Shape (hollow structural section), the angle, the channel and the tee. Structural steel bars, rods and plates are also generic steel building sections. Regular steel beams are formed either by a rolling strategy (hot, cold or extrusion) or a welding method. The American Society for Testing and Components (ASTM) has established the US structural steel standards and identification program. Every single label starts with an "A" and is then followed by two, three or four numbers that classify the material by alloy sort, strength, corrosion resistance and other qualities.