What does the steel designation "C 12 x 20.7" signify?

The designation "C 12 x 20.7" specifically identifies characteristics of a structural steel channel. In this context, the letter "C" indicates that the shape is a channel. The number "12" represents the nominal height of the channel in inches, which is a critical measurement for determining its fit and functionality in construction applications. Finally, "20.7" refers to the weight of the channel, measured in pounds per foot, which is essential for assessing the material's load-bearing capacity and structural integrity.

Understanding these designations is key in construction and engineering, as they ensure that the correct materials are utilized for safety and performance standards. The other choices misinterpret these specifications, leading to confusion about the dimensions and properties of the steel channel. For example, dimensions like width, gauge, or tensile strength are not represented in this designation, which clarifies why those options do not accurately reflect the meaning of "C 12 x 20.7."