Most include tie down straps for attachment.
How to tie things down on a roof rack.
With the cargo on your roof lay the safety strap across the width of your cargo.
Use ratchet or cam straps to tie the roof rack through the doors not the windows.
Simply wrap each strap around a solid anchor point thread the strap through the buckle and pull until secure.
The second option is the side racks.
If you have side rails the most important thing is to reduce the amount of drag the item will make by placing the front of it in line with the beginning of the roof or moving it as far back as you can.
Both water resistant and waterproof bags are available.
Next pull the long end of the strap under the crossbar on the.
With the third option crossbars with side rails you can secure an item to the side rails and run tie downs from front to back securing them to the crossbars.
In the case of a bare roof you re somewhat limited but in this situation it s ideal to have the object centered with the doors of your car so the bulk of the item is most securely strapped down.
First loop the strap under the roof rack s crossbar and drape the loose ends over your oblong load i e.
Use the front and rear corners of the roof rack for your anchor points.
2 take an end of the safety strap and loop it down under a roof bar that runs perpendicular to your vehicle and then back up to the top of the cargo.
Use a tie down that wraps around the item and the rails.
Some roof bags mount to roof racks or raised side rails some mount to roof baskets and others mount to naked roofs.
Create an anchor point for your ratchet straps by looping the hook end around the corner of a crossbar on your roof rack.
Roof racks have been known to fail at high speeds with lots of updraft so take the extra precaution of tying the roof rack down to the roof of the vehicle as well.