Only US firefighters and repairmen can use the buttons to speed up the door-closing process if they have a code or special keys.

只有美国消防员和维修人员有密码或者特殊的钥匙时，他们才能按按钮加速关门的过程。

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You can fold it in half just like closing a book.

你可以像合书一样把它对折。

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By doing this, it can omit the closing tag of an element.

通过这种方法，它可以省略元素的结束标签。

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