Uses of [◯]{まる} symbol in Japanese typography


What is [◯]{まる} symbol is typically used for?

The only usage I know of is the "correct" mark. But the dictionary says it is
also used as a placeholder and for censorship, see
[◯](http://jisho.org/word/%E2%97%8B) and
[◯◯](http://jisho.org/search/%E3%80%87%E3%80%87%20%E3%81%BE%E3%82%8B%E3%81%BE%E3%82%8B).

Here are more detailed questions:

  1. Are there any other uses?
  2. Where can I typically see those?
  3. Can it be used in grammar/spelling tests as a "fill the blank" for kanji?




I usually see ○○ when people refer to a series of related things with similar
names. For example, here is an
[article](http://dic.nicovideo.jp/a/%E5%8D%B1%E9%99%BA%E3%81%AA%E2%97%8B%E2%97%8B%E3%82%B7%E3%83%AA%E3%83%BC%E3%82%BA)
about 危険な○○シリーズ, which is a series of comical video remixes that use the same
song and are typically called 危険な[something].

Also on the Internet it can be used for self-censorship (often comical I
think), like ち◯こ instead of ちんこ.

I've also (rarely) seen people using ●● instead, not sure if there is a
difference.




I usually see ○○ when people refer to a series of related things with similar
names. For example, here is an
[article](http://dic.nicovideo.jp/a/%E5%8D%B1%E9%99%BA%E3%81%AA%E2%97%8B%E2%97%8B%E3%82%B7%E3%83%AA%E3%83%BC%E3%82%BA)
about 危険な○○シリーズ, which is a series of comical video remixes that use the same
song and are typically called 危険な[something].

Also on the Internet it can be used for self-censorship (often comical I
think), like ち◯こ instead of ちんこ.

I've also (rarely) seen people using ●● instead, not sure if there is a
difference.

