Planting a Christmas tree and an American Flag using a truck crane, is symbolic of completion of the project, known as the "Topping Out" ceremony. The practice of "topping out" a new building can be traced to the ancient Scandinavian religious rite of placing a tree atop a new building to appease the tree-dwelling spirits displaced in its construction.
To attach a beam to a structure, a bull pin used to line up the slots on the beam, then the bolts are used to secure the beam ("red on the thread", means its tight enough), using the spud wrench.
Once attached, the beam is secure with the choker cable.
Iron workers are known as the "Cowboys of the Sky"