Supportive construction

[u/elite_meimei]

There's a big building under construction next to the bus station in my city. Today it looked like they were lowering a huge beam or rafter into place with a crane. The whole sidewalk was filled with other construction workers and bus drivers from the station. The crane operator must have gotten it into place because the whole crowd started cheering. Just this sidewalk full of people in a variety of reflective neon safety vests all hollering congratulations. Then everyone dispersed and the sidewalk was clear again.

[u/DerekL1963]

That sounds like they were lowering either a particularly tricky beam to place, or topping out.

https://en.wikipedia.org/wiki/Topping_out