One of the nice things about Mac OS X is that you can assign various useful functions to each of the four corners of your screen, known as "hot corners". When you flick your mouse pointer into a hot corner, you activate the function.

To set up your hot corners in Mac OS 10.5 (Leopard), click the Apple menu and choose System Preferences, then choose Expose & Spaces in the System Preferences window. You'll see the four hot corners in the "Active Screen Corners" section at the top of the window. Each corner has a pull-down menu; choose a function from the menu to assign it to that corner. To disable a hot corner, choose the "-" option at the bottom of the menu.

The available functions are:

• All Windows: Reveals all application windows using Expose
• Application Windows: Reveals just the windows of the active application in Expose
• Desktop: Reveals the Desktop
• Dashboard: Brings up the Dashboard and its widgets
• Spaces: Displays all your Spaces windows (if you have Spaces activated)
• Start Screen Saver: Instantly puts the Mac into screen saver mode
• Disable Screen Saver: Prevents your screen saver starting as long as the mouse is in the corner
• Sleep Display: Instantly turns off the display, leaving the Mac itself awake. (This is a great new feature of Leopard.)

If you find that you accidently trigger your hot corners when you do not want to, you can assign one or more modifier keys to each corner. That way, you have to move the mouse to the corner while also holding down the modifier key (s) in order to activate the corner's function. To assign modifier keys to a corner, hold down the key (s) you want to use while you choose an option from the corner's pull-down menu. You can choose from Control, Option, Shift, Command, or a combination of any of these keys.

Once you get used to hot corners, you'll find that you can quickly activate these essential functions without having to reach for the keyboard. It's a great way to increase your productivity.