Border thickness in smart theme

[Samba]

Hiya!

Just wondering how I could increase the thickness of the line that surrounds the sidebars and main central section in the smart theme...

Could anybody point me in the right direction please? (In very simple terms coz I'm very new to version 8).

Many thanks

[jont]

Is this post of any use http://community.actinic.com/showthread.php?t=33431