Custom Div - Class like Sidebar Block

[PET]

Hello,

I have a custom Div and I want to make it look like a sidebar block but I don't know the actual Class to give to the div. Any ideas?

The class I'm talking about is the "sidebar block". If you click on Forum Block Manager and you enable a sidebar... you will see it. Well that div looks pretty nice but I can't find the class name so I can apply the same style to another div.

Thanks