Abseiling systems are used to access buildings where a BMU is not feasible. The abseiling pipe rail is installed along the perimeter of the building. One end of the rope will be positioned on the stainless steel pipe rail and from this point the abseilers lower their ropes to reach the facades they need to clean. The rail is fixed to the steel support structure at roof level.
You may use the abseiling system instead of a something like a cradle when you have a very specific job that only requires one person and not necessarily a two or three-person job. If there are multiple people working on one job, each person will have their own harness and pulley to get them to the side of the building. The abseiling system allows for a person to get to the specific place of cleaning or repair and return back to the roof.
If you decide not to go with the cradle system, the abseiling system will do just as well. It may be a little scarier for the workers, but they will be fine see as how they already have a since of adventure doing this kind of work in the first place.