Press ALT-F2 to get the run dialog, then type
`gnome-screensaver-preferences`. You'll see a checkbox for locking the
screen.
Interestingly, the screensaver preferences do not appear in the menu by
default. Somewhat understandable since screensavers have really been
superseded by monitor power saving, but the gnome-screensaver is still
used to facilitate.
--
Chris Irwin
e: ch...@chrisirwin.ca
w: http://chrisirwin.ca