Mounting a Thule roof rack on your car is a relatively easy job that can be done in under an hour with no tools. These instructions were written for installing a Thule 450 Crossroad rack on the factory installed rails that come standard on many station wagons and sports utility vehicles. These instructions will work on many other Thule rack systems as well.

[edit] Steps

Image 1 - Basic Rack Parts

Buy the necessary parts from a local retailer or over the Internet. The load bars and railing feet are pictured in Image 1.
Image 2 - Center Foot on Rail

Slide the railing feet onto the load bars. Center the small black triangle of the railing foot in the middle of the installed rail as seen in Image 2.
Place the load bars on top of the factory installed rails of your vehicle. The load bars should be at least 2 feet apart and completely parallel to one another.
Image 3 - Insert Strap in Foot

Wrap the rubber strap around the factory installed rail and place the end into the railing foot as shown in Image 3.
Image 4 - Tighten Strap

Place the allen wrench with the plastic Thule logo into the railing foot and tighten as much as possible as displayed in Image 4.
Insert the allen wrench with the plastic Thule logo into the hole beneath where you tightened the strap. It will slide all the way into the hold and snap shut.
Image 5 - Place end caps

Place the end caps on the load bars as seen in Image 5.

[edit]Tips

After completing the basic Thule roof rack assembly you can install optional parts specifically built to hold skis, surfboards, kayaks, and luggage. Alternatively you can just strap these items to this basic rack with inexpensive nylon straps.
Thule also sells locks to prevent the theft of your roof rack system.