This is really brilliant use of drones. It could be used at so much places where men can not go easily. You'll see for drones with rope starting to build a nice little rope bridge. The tricks to make this possible is the use of rope made out of Dyneema, a material with a low weight-to-strength ratio and thus suitable for aerial construction. Of little weight (7 g per meter), a 4 mm diameter rope can sustain 1300 kg. If you want more information on how this works you can go read the description which is very detailed.