Roof racks are best in terms of versatility and they
can carry loads and loads of bulk, be it sports gear or sheets of
plywood, ladder and many more. In addition, you can even think of
carrying huge cargo boxes. Now products such as roof racks,
bike carriers are used for several purposes. One is the recreational
use, where they are fit onto personal vehicles such as vans and SUV's in
order to attach adventurous gears such as bikes, kayaks, skis and much
more.
Other than recreational use, these racks are even used for commercial vehicles especially designed for heavier loads such as, Boat Roof Racks, pipe clamps, ladder clamps, and load stops.
Source:- http://roofracksydney.tumblr.com/post/131734489692/effective-uses-of-buying-roof-racks