Besides the Lock Screen Button on the K Panel, there is another way you can invoke the K screen savers: Go into the screen saver settings (Application Starter > System > Screen Settings) and click on one of the corners of the sample screen. Three options will be presented. Ignore will ignore any movement of the mouse into that corner. Save will invoke the screen saver after the mouse pointer resides in the corner for more than 5 seconds. Lock will do the same as Save, but it will ask for your login password.