Some common channel iron sizes include C 15 x 40, C 9 x 20, and C 3 x 6. The channel iron notation C 9 x 20 means the beam is 9 inches deep and weighs 20 pounds per foot. A full size list can be found at EngineeringToolBox.com.
A channel iron is a rolled-steel bar with a U-shaped cross section and is also known as a structural channel or C-beam. They are made with a wide base and two shorter rims. Channels are often used in construction and civil engineering. They are either mounted to another flat surface or welded together back-to-back to create a nonstandard I-beam.