So one thing that came out of our recent chat meeting was that (and I'd sort of guessed this by nosing at people's profiles to work out how much SE-wide experience you have) some of our high rep members are unsure about how the close vote system works. So, I'm going to take this opportunity to write up a guide here on meta.
Rationale: why do we close questions?
There are really two ways to do moderation. If you've been on any of the
SE is slightly different - it works the other way. Anyone can ask a question on SE and closing a question is the equivalent of putting that question back into review/improve mode. It's a feedback mechanism designed to react to problem cases only, so the usual business of asking and answering good questions can just... happen.
Why do we close a question?
The philosophy of SE is that each site handles questions on problems you face or things you are trying to understand. The don't ask section of the help center gives you a good overview of things that don't work - to summarise:
These have been worked out over time and with a lot of experience from Stack Overflow and are, broadly speaking true. Sometimes, exceptions are made - it is always a case-by-case thing.
Is closing like deletion?
No. Actually, deletion is a different concept on SE. Closed questions are put "into improve mode" if you like, and are still visible for anyone to improve. That's the idea. Deleted questions are different — they have a red background and are invisible to all but high reputation users. So deletion is different and solves a slightly different problem.
What are the requirements for closing a question?
If you have 3000 reputation, or 500 reputation on a beta site, you can vote to close any question for the reasons above. More on that in a moment.
If you do not have this level of reputation, you will find that under the flag menu, you have an option "this question does not belong here". That will raise a flag for users who can vote to close.
Why can anyone vote to close/reopen?
Firstly, anyone with sufficient reputation can vote to close or reopen (or flag as such, with lower reputation) because it is your site. This is really important - it's about expressing what you feel works and doesn't.
Ok, so how does it work?
Ok, the important piece. Voting to close works like this:
How does vote to re-open work?
A closed question has a "reopen" link underneath it. If you click this, a dialog box will ask you if you are sure - click yes and your vote will be registered to re-open the question.
Below, you can see an example of the re-open link with two votes registered for re-opening (out of five).
What happens if I make a mistake?
Don't worry! You can retract your close vote by clicking the “close” button again. This is useful, for example, if the question has been edited since you voted to close. Note that you cannot use this to change the close reason (if you retract a close vote, you can't cast a new one).
Furthermore, unless five people agree, or a moderator agrees, the question won't be closed.
Why are some questions closed with fewer votes?
Moderator close votes complete the required vote count immediately, no matter how many people have voted. This applies for both close/reopen votes.
Furthermore, closure as duplicate can be faster for two reasons. If the asker agrees that their question is a duplicate, they can validate the closure immediately. This shows a final duplicate close vote from “Community”. Also, if a user with a gold tag badge in one of the question's initial tags votes to close or reopen as a duplicate, this takes effect immediately; in this case a gold tag badge icon appears after the closer's name.
I've seen a closed question and I disagree. What can I do?
Well, one option is to use your re-open vote! You can also always raise a discussion here on meta to seek clarification on why a question is closed and hopefully either a resolution will be reached, or you will get an explanation for the closure.
My name appears on the bottom. Isn't this going to cause problems with other users?
Actually, surprisingly few closed questions generate any response at all.
However, if you experience difficulties as a result of closing a question, you can and should contact a moderator via the flag mechanism (which is anonymous). We can then take any necessary action.
How do I find questions I might need to close? What about re-opens?
In the review queues, specifically the close votes queue and the reopen votes queue. These queues are open to everyone who has the close vote privilege. For each question, you get to decide whether to close/reopen or not; enough “no” votes take the question out of the queue. An edit from the queue is a vote to not close or reopen.