If the part of the lock that goes into the frame isn't visible when locked, what does it mean?

Sounds like the lock is broken.

It sounds like you’re talking about a deadbolt lock. Can you look up some images and see if one looks right to you? Or at least say the brand (and model number if you have it) of the lock that you’re talking about, so we can discuss it sensibly?

And by “visible” – on a deadbolt lock – I’m presuming that you mean the deadbolt itself as seen from inside the door (because you should never be able to see it from outside – a deadbolt that can be “seen” can also be “sawn” – literally, with a hacksaw). But from inside the door, between the door’s edge if it doesn’t butt up to the jamb perfectly, you ought to be able to see the bolt slide in and out of the jamb / frame as it is operated. If it’s not operating at all, then it’s broken.

If the locking is “done”, and the bolt shoots home, whether you can see it or not and whether it seems to turn the way it ought to or not – and assuming it can still be unlocked normally, both from inside and outside (with the key) – then it sounds like it is working properly.

It’s not a lock that requires a key to open from inside, too, is it? Some extra-security doors require a key from inside for passage outside, too. (It’s a potentially lethal fire hazard, but it sure is secure.)

But what have you got? (It would also be helpful if you can look at an image on the web where the parts of the lock – and door – are illustrated / named / described so that this discussion can be done most helpfully and least painfully.)

@CWOTUS Thanks. It’s a toilet in an institution. There is no key involved. It works fine by the way. The thing is if somone forgot that they locked it already, by turning it again, they would be unlocking it. Noooo good. This one looks almost the same.
http://www.entrostyle.com.au/locks-and-latches
The second one going southward or fifth going sideways.
Or
http://tinyurl.com/jumh55y (Give it 2 seconds)

@CWOTUS sorry I forgot to post the long version of the last link

https://www.google.ca/search?q=images+door+locks&biw=1184&bih=531&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwiIo8mMu5nNAhXH0h4KHSPeAyQQsAQIGg#imgrc=TQFqcnyd33WFmM%3A

Just guessing here but I would say if the bolt is not visible it is either because the door and frame are tight and no gap exists or that there is some kind of protective shield in place that hides the bolt and reduces the chance of it being jimmied open.

As for which way it turns to lock it, that depends on how the lockset is installed. Many times the part that goes through the door into the cylinder and operates the bar is not centered, if this is the case installing it above the centerline means you have to turn the latch one way and below the centerline takes the opposite motion. This could be by design or it could be that someone installed it upside down.

In my limited experience of locking and unlocking things, clockwise has always been used to do the locking and counterclockwise for unlocking.

@LostInParadise with locks it is usually toward the strike side (not the hinge side) is locking and away from is opening so it changes depending on which side the door is hinged on.

That makes sense. Now that I think of it, the passenger side doors on cars are the reverse of driver side doors.

As @rojo was so close to saying more accurately: the lock / bolt always has to shoot toward the strike plate to engage the lock; it’s how they work, after all. The question is whether the door opens left or opens right; that is, whether the hinge side of the door is on the right (facing the door from the inside of the compartment) or on the left. Depending on which side of the door the lock is to be installed, the same lock can be turned right side up for one side, or upside-down on the other.

It’s not a high security lock. In fact, in this application it wouldn’t be. (I don’t know whether that’s a building code issue or just common sense, especially since disabled people may occasionally require assistance in exiting. It must be possible to open the door from the outside without resorting to breaking the lock or the door.)

But to get back to your question: when the bolt isn’t visible from the inside of the compartment, it only means that the door fits flush with the jamb, so there’s no opening left to enable a view of the bolt. (A common practice upon exiting such a compartment is to leave the lock “shot”, so that the bolt won’t allow the door to close and leave people wondering whether the compartment is occupied or not. I recommend adopting that practice.)

I appreciate everyone’s answer.

@CWOTUS
”... so there’s no opening left to enable a view of the bolt.” There is a gap/opening though. locked or not locked it’s the same there is nothing there. There is just no bolt visible where it normally is. So how about the need to ensure that the door is locked? I mean the senario I gave in my last post?

@rojo
”...some kind of protective shield in place that hides the bolt and reduces the chance of it being jimmied open.” There is no protective shield. I see that if robbery is the goal, but a toilet?

…I meant if the prevention of robbery is the goal.