- Open the Keychain Access application (/Applications/Utilities/Keychain Access).
- Open the Preferences panel (menu: Keychain Access->Preferences).
- Make sure "Show Status in Menu Bar" is enabled.
- Now close the Preferences panel and then the Keychain Access application.
The next part of this hint involves assigning a keyboard shortcut that will activate the Lock Screen option of the Keychain Access menu extra.
- Start System Preferences (/Applications/System Preferences).
- Click on Keyboard & Mouse.
- Click on the Keyboard Shortcuts panel.
- Under Application Keyboard Shortcuts -> All Applications, click the "+" sign (lower left corner) to add a shortcut.
- For Application, choose All Applications.
- For Menu Title, enter Lock Screen
- In the Keyboard Shortcut field, press Control-F9 (press the Control key first, hold it down, then press the F9 key), then click Add.
- Before leaving the Keyboard Shortcuts panel, scroll up and find the "Move focus to status menus in the menu bar" entry. On my default install of Tiger 10.4.1, this shortcut is defined as ^F8 (Control plus the F8 key).
[robg adds: You can skip the logout/login step if you open the Terminal and type killall SystemUIServer. When I wanted a fast way to lock my screen, I used Butler to create a keyboard shortcut to the login window -- when I press my shortcut keys, up pops the login window. However, the method in this hint works, doesn't require any third-party software, and it's free...]

