How are electricity cables taken up on the roofs of tho high apartment buildings?
Highly possible that one guy used a bow to shoot an arrow tied to end of a ball of string. As the arrow flew to the position of the other guy the string feed smoothy off the ball. In no time the two fellows had a length of string between themselves.

If it was a windy day then one guy possibly launched a kite out into the breeze. By running the kite out a good length the second guy was able to catch the kite string in hand.

In any case with the string between them then a light weight rope is tied to one end and the other guy used the string to pull the rope across the gap. The light rope is then used to pull across a stout rope. 

Now you can guess that the stout rope, being strong and durable, is used to pull the electrical cable across between the buildings!!