My thule cargo box does not allow me to remove the key when the lock cylinder is in the unlock position a search lead me to a forum thread saying i have to use my key to turn the lock about 15 degrees remove the key the universal change key and then remove the lock cylinder i hope this will help some folks out there.
How to remove thule roof rack lock.
Turn the lock to the unlock position using the regular locking key.
If you cannot find the master key that came with your thule product you can obtain one at a local thule retailer or by calling thule at 800 238 2388.
Press your finger against the lock cylinder to keep it in place and use your other hand to pull out the master key.
Obtain a master key.
Unlock the outer housing or lockable knob at the base of the feet using the thule key that came with the set.
Insert the master key into the cylinder all the way until you hear a click.
Once it s inserted fully a quarter turn clockwise should lock in place the mechanism for instance one of the four feet of a car roof rack.
Open the doors on both sides of the vehicle below where the roof bar is mounted.
Remove the master key and try the locking key.