Drywall and Plywood Cartop Carrier / Roof Rack

Step 4 Add the Rails

Lay the 8 foot 2x2's on the cross members. Center them fron to back so that your load will put equal pressure on all four feet. You will notice, again, that due to the curve of the roof the rails do not lay flat on the cross members.
Try to allign your cross members and rails so that they are square. You can use your car for reference.
Use a shim or scrap wood to fill the gap while you drive two screws from each rail into each cross member.