How to Tie Things to the Top of Your Car
Stack items evenly across your roof, or roof rack if you have one. Place heavier items on top of lighter items to help hold them down.
Cover the load with netting or a tarp to prevent items from shifting or falling out.
Use a tie-down strap to prevent items from shifting front to back. Attach the tie-down to your vehicle's frame or roof rack. Do not attach the tie-downs to your bumper.
Use 1-2 additional tie-downs to secure items from shifting left to right. If you don't have a roof rack, run the tie-down through the car's open windows and attach the hooks together inside the car.
From the pioneers who strapped armoires to wagons, to the Great Depression-era farmers who roped pianos to Model Ts, the tradition of loading up your ride with oversized items and cruising across the country is a rich one. Mattresses, kayaks, lumber, or simply suitcases that won’t fit in the trunk — whatever it is that doesn’t go in your car can often be carried on top, provided you take the right precautions and make sure your load is latched on.