I've used the term; so do many others. The term? I-Beam.
While it's commonly used to describe a type of structural steel, there is no designation "I" for describing a steel section shaped like an "I". The descriptions are "W" and "S", with the W shape a designation for wide-flange beams more commonly used for steel construction. S shapes aren't that common, since they don't have the same strength characteristics of W shapes and the inner part of a W shape is not as severely sloped as that of an S shape.
Now you can sleep better at night. I know such things bothered you to the point of restlessness.
In Case You've Wondered
My blog is where my wandering thoughts are interspersed with stuff I made up. So, if while reading you find yourself confused about the context, don't feel alone. I get confused, too.
If you're here for the stories, I started another blog: scratchingforchange.blogspot.com
One other thing: sometimes I write words you refuse to use in front of children, or polite company, unless you have a flat tire, or hit your thumb with a hammer.
I don't use them to offend; I use them to embellish.