My back door (which is only two years old) has a door knob that recently suddenly stopped turning. I can lock and unlock it, but it just won't turn. Here's a picture of the inside of the door knob:
The very center bit is the lock mechanism, and I can turn it (locking and unlocking it) easily with a hex key. The half-circle immediately next to it appears to me to be the mechanism for opening the door — I could be wrong about that, though. It will not budge. The only two options I can see now are:
taking the door off its hinges so that I can completely remove the lock set and possibly replace it with a new one; or
calling a lock smith.
I'm more inclined to go with the latter than the former. Any other suggestions?