<P> The structural channel, also known as a C - beam or Parallel Flange Channel (PFC), is a type of (usually structural steel) beam, used primarily in building construction and civil engineering . Its cross section consists of a wide "web", usually but not always oriented vertically, and two "flanges" at the top and bottom of the web, only sticking out on one side of the web . It is distinguished from I - beam or H - beam or W - beam type steel cross sections in that those have flanges on both sides of the web . </P> <P> The structural channel is not used as much in construction as symmetrical beams, in part because its bending axis is not centered on the width of the flanges . If a load is applied equally across its top, the beam will tend to twist away from the web . This may not be a weak point or problem for a particular design, but is a factor to be considered . </P> <P> Channels or C - beams are often used where the flat, back side of the web can be mounted to another flat surface for maximum contact area . They are also sometimes welded together back - to - back to form a non-standard I - beam . </P>

What is the difference between c channel and mc channel