Today’s invention is a way to ensure a public toilet cubicle door stays closed, even when the lock is broken, as is often the case, these days.
Design considerations include pocketability and the need never to handle anything which has touched the cubicle or, heaven forbid, the floor.
I give you…the C clamp. As shown, this is cheap, and would be easily carried by travellers, involve no skin contact with the door (grey) or walls (blue) and be visible to people who will not see any ‘engaged’ sign if the lock is broken.
Also, it would be almost impossible to undo from outside.