They should be just stuck on with double sided foam tape (same kinda stuff that sticks your rear view mirror to your wind screen)

It's horrible stuff to remove. Best way is to get some thread and loop it over and make a sawing motion to remove the strips. You'll be left with a guey residue which is horrible to remove, you have to just rub it with your thumb and a bit petrol on a cloth. Try a hairdryer too to heat the tape up and remove it.

Hope this of use