easy to use, but not sure of the red button to alert you if TSA checked your luggage.  There is a button on the top of the lock that you press down. If TSA unlocks the lock the button is supposed to pop up to alert you the lock had been opened by TSA. We got our luggage back from our flight and the button was down but inside the suitcase was a paper flyer informing me the suitcase was checked by TSA...not sure why the button did not pop up.