My bars are the thule aero bars with a foot pack that clamps onto the car’s full length roof rails.
Taking my roof bars off last night, I couldn’t get one to undo, the handle kept slipping on the bolt head.
It occurred to me that there might be a hex head under the plastic which is just clipped on over the bolt. There was and the problem was solved. But as it was so obviously easy to remove a plastic cover to undo a bolt, without breaking anything, what is the point in the lock? Surely that just overcomplicates things!?

It always seemed obvious to me that the locks on those are nothing more than gesture. Surprised anyone would think otherwise!

I never relied on them for bike security, obvs. Just thought they might offer a bit more than simple unscrewing them.

They might persuade the casual thief to go elsewhere but it doesn’t take much to get through to them.
My last van came with thule roof bars but no key to the metal covers, a lump hammer and a cold chisel got me access to the Allen bolts under the locks with little fuss.