Using your MacBook or MacBook Pro with the lid closed. Really.

As the prices for large, flat-screen displays continue to fall, many folks are buying one as a second display. About a year ago, I wound up with a 23″ Apple Cinema Display that I’d bought used from a friend who was moving. I installed it in my Phoenix office, with the idea that I’d use it with my laptop — then a 15″ MacBook Pro; now a 13″ MacBook Pro. I connected the display to my Mac and began using it with the laptop’s built-in display, very much as I discuss here.

I soon realized that I really didn’t use the second display because of the awkwardness of “driving” the mouse from one screen to the other. But, at the same time, It made no sense to use the smaller monitor when I could be using the larger one. When I started using a wireless keyboard and mouse with my laptop in my Phoenix office, I realized that I was ready for clamshell mode.

Clamshell mode enables you to use a PowerBook G4, MacBook, MacBook Air, or MacBook Pro with the computer’s lid closed. All you need to have is an external monitor and input devices. The input devices can be wired or wireless. The computer sends all display output to the external monitor and accepts all input from those external input devices. The computer itself just does the CPU stuff.

You can even put the computer aside, out of the way. The photo here gives you an idea of how my office desktop looks with my 13″ MacBook Pro running in clamshell mode, standing in a special stand I bought to keep it out of the way on my rather shallow desk.

There are two ways to enter and exit clamshell mode, depending on whether your input devices are wired or wireless. Let’s take a look at each method.

Wired Input Devices

If you have a wired keyboard and mouse, getting set up with clamshell mode is pretty easy.

1. Connect the computer to a power adapter — this won’t work on battery power — and, if necessary, turn your computer on.
2. Plug in your keyboard and mouse.
3. Connect your external display to your computer and turn it on.
4. When the desktop appear on the external display, close the computer’s lid.
5. If the computer goes to sleep — which is likely — wake it by touching any key on the keyboard.

You can now use the computer with the external keyboard, mouse, and display.

Wireless Input Devices

In my particular setup, I have a Bluetooth Apple keyboard and a wireless (but not Bluetooth) Logitech mouse. The instructions I follow are similar to the wired input devices instructions. The key is to pair any Bluetooth devices before starting clamshell mode.

1. Connect the computer to a power adapter — this won’t work on battery power — and, if necessary, turn your computer on.
2. Make sure Bluetooth is turned on.
3. Pair and connect your computer with your keyboard and mouse and confirm that they work.
4. In the Advanced settings of the Bluetooth System Preferences pane, make sure the Allow Bluetooth Devices to Wake this Computer.
5. Connect your external display to your computer and turn it on.
6. When the desktop appear on the external display, close the computer’s lid.
7. If the computer goes to sleep — which is likely — wake it by touching any key on the keyboard.

In my case, because my mouse is not Bluetooth, I had to connect the mouse’s USB wireless adapter to my monitor (which has USB ports) or computer and turn the mouse on.

Watch the Video

If you’re a visual kind of person and want to see the process in action, watch this video, which I shot with my Flip camera. We’re not talking Academy Award material here, folks, but it does show you how it works — at least for me.

When You’re Finished with Clamshell Mode

Eventually, you’ll want to start using your computer the usual way, with its own built-in display. Here’s how you do it:

1. Put the computer to sleep. (This step might not be necessary; it depends on the computer model and display. Experiment with your system.)
2. Disconnect the display.
3. Wake your computer to use it.

Need More Information?

You can find more information about using monitors and Bluetooth devices with Mac OS X 10.6 Snow Leopard in Mac OS X 10.6 Snow Leopard: Visual QuickStart Guide.

You can find Apple’s instructions for using clamshell mode here. That document will be revised as procedures change.