How to set the width of the forum?

[hitmann]

Could you please tell me how to set the space between the forum and the background border like this:

http://i28.tinypic.com/2ururdf.gif

[Hayk]

Admin CP > Styles and Templates > Style Vars > Main Table Width (pixels or percentage)

[hitmann]

That changes the width of the whole forum page. What I'm looking for is more space between the white background border and the forum border

Edit: ok got it, it's Spacer Size value