User Flag (Search=>Filter=>General)
Use these check boxes to select (or exclude) waypoints for which you have set a user flag. By default, all waypoints are included in the filter. You must select at least one check box or the filter will fail.
The user Flag enables you to manually select individual waypoints to perform some action on (for example, to delete a group of waypoints or only send those waypoints to your GPS or Export to Mapsource). You do this by setting the user flag (just click your mouse in the box) then set a filter on "User Flag" = Set