Hello Lokimeister,
I understand that you would like to know where the Close File icon in the tool bars is located for AutoCAD LT 2010.
Many users have become accustomed to using either the command line CLOSE or the 'X' on the drawing file to close the file, but if you would like this icon to be in your tool bars, there is a way to create this and place the button on the tool bar.
I have created a Jing video that shows how to make the close icon for the toolbar and I will provide written steps as well for the process of creating the icon.
NOTE: This video has NO audio.
2010-04-20_ACADLT10_CloseBtn
Steps to create a Close icon for your tool bar:
NOTE: The steps provided below are shorter and slightly different then provided in the video.
1. Launch AutoCAD LT 2010.
2. Type CUI, press Enter.
3. With the Customize tab selected in the Customize User Interface dialog box, in the Command List> Search command list, type CLOSE.
4. Select the 2nd Close command.
5. In the Button Image, scroll to an icon image you wish to use for the Close button, click Apply.
6. Drag the Close icon to the Quick Access Toolbar at the top of the ACADLT window, click Apply then click OK.
The above are two different ways to create the Close icon.
You can also do as Dean suggested for the Close:
"Menu selection:
http://docs.autodesk.com/ACD/2010/ENU/AutoCAD%202010%20User%20Documentation/files/WS1a9193826455f5ff...
or
Make one button.
or
Type it.
or
Create a shortcut tied to mouse button or keyboard key combo."
Please let me know if this helps with your question.
Best Regards,
Kathleen McCann
Autodesk Product Support