中键的快捷键使用：
选择文本--移动鼠标--中键（即粘贴选择的文本到鼠标移动的地方）
1. One common shortcut is to paste selected text. (This is sometimes called primary selection paste.) Select the text you want to paste, then go to where you want to paste it and middle-click. The selected text is pasted at the mouse position.
注意：粘贴文本用中键 与 clipboard完全分开的。
Pasting text with your middle mouse button is completely separate from the normal clipboard. Selecting text does not copy it to your clipboard. This quick method of pasting only works with the middle mouse button.
滚动鼠标， 也可以中键鼠标在一个空的地方 来移动到确定的位子。
2.On scrollbars and sliders, a regular click in the empty space moves by a set amount (such as one page) in the direction you clicked. You can also middle-click in the empty space to move to exactly the location you clicked.
中键 打开一个应用（如果已经打开了一个应用，他新开一个)
3. You can quickly open a new window for an application with middle-click. Simply middle-click on the application's icon, either in the launcher on the left, or in the dash.
中键一个链接， 在一个新到tab中打开。
4. Most web browsers allow you to open links in tabs quickly with the middle mouse button. Just click any link with your middle mouse button, and it will open in a new tab. Be careful clicking the link in the Firefox web browser, though. In Firefox, if you middle-click anywhere except on a link, it will try to load your selected text as a URL, as if you used middle-click to paste it to the location bar and pressed Enter.
中键打开一个文件夹 在新到tab中。 中键打开一个文件。
5. In the file manager, middle-click serves two roles. If you middle-click a folder, it will open in a new tab. This mimics the behavior of popular web browsers. If you middle-click a file, it will open the file, just as if you had double-clicked.