"What does your handle mean?"
W10x12 is a size of wide flange beam (see avatar). UNO is an abbreviation for "unless noted otherwise".
In a structural framing layout for a building, sometimes a large portion of the beams are all the same size and it's simpler to not call out the sizes on "typical" beams. So you see page notes like "Beams are W10x12 UNO".
I'm a nerd for structural steel and I intend to spread the joy of steel detailing to the best of my ability.
"I appreciate SDF but it's a general-purpose server and the name doesn't make it obvious that it's about art." - Eugen Rochko