http://69.10.233.10/KB/cpp/MBtn2DblClickVC.aspx
A scroll button or mouse wheel.
Press both mouse buttons at the same time.
Middle Mouse Button Cheers
-7-(-3)
The middle mouse button is usually the scroll wheel. Push the wheel down to click it.
Place the mouse pointer over the [x] sign in the tab and click. Or if you are in the tab you want to close, press Ctrl+W Or Use your middle mouse button Mouse over the tab you want to close and press the middle mouse button.
external part are left , middle ,and right mouse button, palm rest.and long wire.
It means a button which is neither the left nor right button on a mouse. Many have a middle button, sometimes in the form of a wheel, that can be pressed down to act as a button. This would be considered Button 3 on a mouse, but some could also have a button positioned where the user's thumb is.
To bind the impulse 101 command to a mouse button in Half-Life, you first need to open the console using the "~" key, then type in "bind mouse3 impulse 101" to bind the command to the middle mouse button (mouse3). You can replace "mouse3" with a different button number to bind it to a different mouse button.
secondary mouse button
The mouse button that is the most used is the 'left side' of the mouse.
you have to press the middle scroll button/wheel on the mouse