No lock, but a lot of the ones I remember had a bifold door with the hinge on the inside, so you could lean against it to effectively keep it shut. It was possible to wedge something in there to keep the door shut, and I think that was the subject of a scene in a slapstick movie, where the poor schmuck trying to use the phone left his briefcase perched on a shelf, and as he left it fell and wedged the door shut. I can’t remember the movie, though.