[openbox] Frame around windows: Width setting

[meino.cramer at gmx.de]

Hi,

the frame around the windows (that what is neither the title bar nor
the area controlled by the application) of my openbox installation is
very very very thin. I need a micrometer to position the mouse cursor
on it. ;)

Where can I configure this frame for more width?

Thank you very much in advance for any help!
Best regards,
mcc