For the fire-wall to be effective, the sheet-rock must be trimmed very precisely to fit around the ceiling joists. Fire rated caulk must then be applied all around to prevent air gaps. The process is repeated twice - once for each layer.
The electrician starts wiring the fuse boxes. The one on the left is 400 Amps, the one on the right is 600 Amps. A lot of the equipment requires 208-230V 3-Phase current.