I have never got to grips with these locks, commonly found on lavatory doors. I first encountered them in a family holiday to a B&B outside Rhyl, a new build that was full of these doors, all disconcertingly similar. The 8 year old me had no idea whether or not the room beyond was accessible to guests or reserved for the elderly couple who ran the house.
I never know whether one pushes the central button to lock oneself in securely. Further, because a simple anti-clockwise twist of the door handle is all it takes to unlock the door, I can never fully trust that doors bearing these locks cannot be unlocked either inadvertently or by design from the outside by some red-faced abject person or some pesky jester.
This particular lock is in a lavatory at the Leela Hotel, Mumbai. I am disconcerted by it every time I come.