The Thule Tracker kit is a simple solution if you're looking for a "factory" look rather than an "add on" look for your car's roof and you don't like the idea of placing "clips" in your door frame, which may or may not deform the weather seal..
The base plates fit a wide variety of factory tracks, which are the long aluminum or hard plastic pieces that run from front to rear on your car's roof.
You have to consult a good Thule dealer to find out which base plates you need, or you can use Thule's website.
Installing the base plates is easy. A simple hex wrench is provided, and you place the base plates wherever you want on your tracks. If you want to move the plates closer or farther apart (ie: kayak or canoe bar placement is different than ski/snowboard rack placement), then you have to use the hex wrench, so don't lose it. The foot and bar combination then simply snaps down onto the plates by pushing the button on the foot (it holds a lock core).
Once installed, it will take you all of 20 seconds to remove your entire rack system, a huge plus. The base plates remain in the tracks, but you can remove them with the hex wrench if you're going to a classic car show or are just anal about appearances. (Get a life.)
The feet and bar combo does wobble just a bit when placed in the tracks without any gear weight like bikes, skis or kayaks, but when the weight of your gear is on board, there's no wobble at all.
This is a nice set-up, similar to Yakima's Landing Pad, but a bit easier to install and remove. Quality between the two brands is equal.
Good stuff. I've been installing them for many years and have never had a complaint about quality, rust, broken parts or bad Karma.